Semiconductor light-emitting device and method for manufacturing thereof

Information

  • Patent Grant
  • 6476421
  • Patent Number
    6,476,421
  • Date Filed
    Friday, April 20, 2001
    23 years ago
  • Date Issued
    Tuesday, November 5, 2002
    22 years ago
Abstract
In a semiconductor light-emitting device, on an n-GaAs substrate are stacked an n-GaAs buffer layer, an n-cladding layer, an undoped active layer, a p-cladding layer, a p-intermediate band gap layer and a p-current diffusion layer. Further, a first electrode is formed under the n-GaAs substrate, and a second electrode is formed on the grown-layer side. In this process, a region of the p-intermediate band gap layer just under the second electrode is removed, the p-current diffusion layer is stacked in the removal region on the p-cladding layer, and a junction plane of the p-current diffusion layer and the p-cladding layer becomes high in resistance due to an energy band structure of type II. This semiconductor light-emitting device is capable of reducing ineffective currents with a simple construction and taking out light effectively to outside, thus enhancing the emission intensity.
Description




BACKGROUND OF THE INVENTION




The present invention relates to a semiconductor light-emitting device having a current diffusion layer and method for manufacture thereof.




In recent years, LEDs (Light-Emitting Diodes), which are semiconductor light-emitting devices, have been in the limelight as indoor/outdoor display devices. In particular, with their trend toward higher brightness, the outdoor display market has been rapidly expanding while LEDs have been growing as a medium to replace neon signs. High-brightness LEDs of visible range in such fields have been developed by AlGaInP-based DH (Double Hetero) type LEDs.

FIGS. 25A

,


25


B,


25


C show a top view, a sectional view and a functional view, respectively, of a yellow-band AlGaInP-based LED as a semiconductor light-emitting device.




In this semiconductor light-emitting device, as shown in

FIGS. 25A and 25B

, an n-GaAs buffer layer


301


(thickness: 0.5 μm, Si doping: 5×10


17


cm


−3


), an n-AlGaInP cladding layer


302


(thickness: 1.0 μm, Si doping: 5×10


17


cm


−3


), an undoped (Al


0.3


Ga


0.7


)


0.5


In


0.5


P active layer


303


(thickness: 0.6 μm), a p-AlGaInP cladding layer


304


(thickness: 0.7 μm, Zn doping: 5×10


17


cm


−3


), a p-AlGaAs current diffusion layer


305


(thickness: 6 μm, Zn doping: 3×10


18


cm


−3


), and a p-GaAs cap layer


306


(thickness: 0.1 μm, Zn doping: 3×10


18


cm


−3


) are grown on an n-GaAs substrate


310


by MOCVD process, and a first electrode


311


is formed on the substrate side while a second electrode


312


is formed on the grown layer side. Regions of the p-GaAs cap layer


306


other than a device center region thereof opposed to the grown-layer side second electrode


312


have been removed. In this semiconductor light-emitting device, having a pn junction formed within the active layer


303


, light emission is generated by recombination of electrons and holes. With this semiconductor light-emitting device molded into 5 mm dia. resin, when a 20 mA current was passed therethrough, the resultant emission intensity was 1.5 cd.




In this semiconductor light-emitting device, as shown in

FIG. 25C

, a current injected from the grown-layer side second electrode


312


expands within the p-AlGaAs current diffusion layer


305


, being injected into the active layer


303


, where most part of the current flows to the region under the second electrode


312


. As a result, light emission over the region under the second electrode


312


is intercepted by the second electrode


312


so as not to go outside, resulting in an ineffective current. This leads to a problem that the emission intensity would be lower.




Thus, as an solution to this problem, there has been proposed a structure in which a current blocking layer for blocking the current is introduced under the second electrode


312


.





FIGS. 26A-26C

show a top view, a sectional view and a functional view, respectively, of a semiconductor light-emitting device having the structure in which the current blocking layer is introduced. In this semiconductor light-emitting device, as shown in

FIGS. 26A and 26B

, an n-GaAs buffer layer


321


(thickness: 0.5 μm, Si doping: 5×10


17


cm


−3


), an n-AlGaInP cladding layer


322


(thickness: 1.0 μm, Si doping: 5×10


17


cm


−3


), an undoped (Al


0.3


Ga


0.7


)


0.5


In


0.5


P active layer


323


(thickness: 0.6 μm), a p-AlGaInP cladding layer


324


(thickness: 0.7 μm, Zn doping: 5×10


17


cm


−3


), a p-AlGaInP intermediate band gap layer


325


(thickness: 0.15 μm, Zn doping: 2×10


18


cm


−3


), a p-GaP first current diffusion layer


326


(thickness: 1.5 μm, Zn doping: 1×10


18


cm


−3


), an n-GaP current blocking layer


327


(thickness: 0.4 μm, Si doping: 3×10


18


cm


−3


), and a p-GaP second current blocking layer


328


(thickness: 6 μm, Zn doping: 2×10


18


cm


−3


) are grown on an n-GaAs substrate


330


by MOCVD process, and a first electrode


331


is formed on the substrate side while a second electrode


332


is formed on the grown layer side.




In this semiconductor light-emitting device, the n-GaP current blocking layer


327


is subjected to etching removal with its device center region left, and the second current diffusion layer


328


is re-grown thereon.




In this semiconductor light-emitting device, as shown in

FIG. 26C

, a current injected from the grown-layer side second electrode


332


, avoiding the n-GaP current blocking layer


327


provided under the second electrode


332


, flows to both sides of the n-GaP current blocking layer


327


. As a result, as compared with the semiconductor light-emitting device shown in

FIG. 25

, this semiconductor light-emitting device involves less ineffective current that flows to under the second electrode


332


, resulting in increased emission intensity. With this semiconductor light-emitting device applied to a 5 mm dia. molded article, the emission intensity at a 20 mA current conduction was 2.0 cd, an increase of slightly more than 30% as compared with the semiconductor light-emitting device shown in FIG.


25


. However, because the thickness of the p-GaP first current diffusion layer


326


provided under the n-GaP current blocking layer


327


is as thick as 1.5 μm, there is still a sneak current going to under the n-GaP current blocking layer


327


as shown in FIG.


26


C. Thus, there is a problem that the ineffective current is not eliminated completely.




SUMMARY OF THE INVENTION




Accordingly, an object of the present invention is to provide a semiconductor light-emitting device, as well as a method for manufacture thereof, which can be reduced in ineffective current with a simple construction and can effectively take out light to outside.




In order to achieve the above object, there is provided a semiconductor light-emitting device comprising: a first-conductive-type first cladding layer, a first-conductive-type or second-conductive-type or an undoped active layer, a second-conductive-type second cladding layer, a second-conductive-type intermediate band gap layer and a second-conductive-type current diffusion layer, all of which are stacked on one side of a surface of a first-conductive-type semiconductor substrate, a first electrode formed on the other side of the surface of the first-conductive-type semiconductor substrate, and a second electrode formed partly on the second-conductive-type current diffusion layer, wherein




a region of the second-conductive-type intermediate band gap layer just under the second electrode is removed, and the second-conductive-type current diffusion layer is stacked in the removal region on the second-conductive-type second cladding layer, and wherein




a junction plane of the second-conductive-type current diffusion layer and the second-conductive-type second cladding layer has an energy band structure of type II.




With this semiconductor light-emitting device having the above constitution, in the removal region of the second-conductive-type intermediate band gap layer, since the junction plane of the second-conductive-type current diffusion layer and the second-conductive-type second cladding layer becomes high in resistance due to the energy band structure of type II, the current flows to around the removal region, allowing ineffective currents flowing under the second electrode formed partly on the second-conductive-type current diffusion layer to be reduced so that the emission intensity is enhanced. It is noted that the first electrode formed on the other side of the surface of the first-conductive-type semiconductor substrate may be either a partial electrode or a full electrode.




Also, there is provided a semiconductor light-emitting device comprising: a first-conductive-type first cladding layer, a first-conductive-type or second-conductive-type or an undoped active layer, a second-conductive-type second cladding layer, a second-conductive-type intermediate band gap layer and a second-conductive-type current diffusion layer, all of which are stacked on one side of a surface of a first-conductive-type semiconductor substrate, wherein




a device center region of the second-conductive-type intermediate band gap layer is removed, and the second-conductive-type current diffusion layer is stacked in the removal region on the second-conductive-type second cladding layer,




the second-conductive-type current diffusion layer and the second-conductive-type second cladding layer have an energy band structure in which an upper-end position of valence band and a lower-end position of conduction band are in a type II relation, and wherein




the semiconductor light-emitting device further comprises a first electrode formed overall on the other side of the surface of the first-conductive-type semiconductor substrate, and a second electrode formed over the device center region on the second-conductive-type current diffusion layer.




With this semiconductor light-emitting device having the above constitution, in the removal region of the second-conductive-type intermediate band gap layer at the device center region, since the junction plane of the second-conductive-type current diffusion layer and the second-conductive-type second cladding layer becomes high in resistance due to the energy band structure of type II, the current flows to around the removal region, allowing ineffective currents flowing under the second electrode formed at the device center region on the second-conductive-type current diffusion layer to be reduced so that the emission intensity is enhanced.




In one embodiment of the present invention, an upper-side portion of a region of the second-conductive-type second cladding layer corresponding to the removal region of the second-conductive-type intermediate band gap layer is removed.




With the semiconductor light-emitting device of this embodiment, both the removal region at the device center region of the second-conductive-type intermediate band gap layer and the region where the upper-side portion of the second-conductive-type second cladding layer opposed to the removal region has been removed become high in resistance, and besides the high-resistance interface of the second-conductive-type current diffusion layer and the second-conductive-type second cladding layer is near the active layer. Thus, the ineffective currents flowing under the second electrode can further be reduced so that the emission intensity is further enhanced.




Also, there is provided a semiconductor light-emitting device comprising: a first-conductive-type first cladding layer, a first-conductive-type or second-conductive-type or an undoped active layer, a second-conductive-type second cladding layer, a second-conductive-type etching stop layer, a second-conductive-type third cladding layer, a second-conductive-type intermediate band gap layer and a second-conductive-type current diffusion layer, all of which are stacked on one side of a surface of a first-conductive-type semiconductor substrate, wherein




device center regions of the second-conductive-type intermediate band gap layer and the second-conductive-type third cladding layer are removed, respectively, and the second-conductive-type current diffusion layer is stacked in the removal regions on the second-conductive-type etching stop layer,




the second-conductive-type current diffusion layer, the second-conductive-type etching stop layer and the second-conductive-type second cladding layer have an energy band structure in which an upper-end position of valence band and a lower-end position of conduction band are in a type II relation, and wherein




the semiconductor light-emitting device further comprises a first electrode formed overall on the other side of the surface of the first-conductive-type semiconductor substrate, and a second electrode formed over the device center region on the second-conductive-type current diffusion layer.




With the semiconductor light-emitting device having this constitution, the removal regions of the device center region where the second-conductive-type intermediate band gap layer and the second-conductive-type third cladding layer have been removed become high in resistance due to the fact that an energy band structure in which the upper-end position of the valence band and the lower-end position of the conduction band are in the type II relation is formed in the second-conductive-type current diffusion layer, the etching stop layer and the second cladding layer. Besides, the high-resistance interface can be formed near the active layer with high controllability by the presence of the second-conductive-type etching stop layer. Thus, there can be fabricated a semiconductor light-emitting device less in ineffective currents and high in emission intensity with a good yield.




In one embodiment of the present invention, the removal region at the device center region of the second-conductive-type intermediate band gap layer and the second electrode have generally identical configurations and are opposed to each other.




With the semiconductor light-emitting device of this embodiment, the emission efficiency can be optimized by the arrangement that the grown-layer side second electrode and the high-resistance region under the second electrode, both having generally equivalent configurations, are opposed to each other. Thus, the ineffective currents can be lessened and the emission intensity can be enhanced.




Also, there is provided a semiconductor lightemitting device comprising: a first-conductive-type first cladding layer, a first-conductive-type or second-conductive-type or an undoped active layer, a second-conductive-type second cladding layer, a second-conductive-type intermediate band gap layer and a second-conductive-type current diffusion layer, all of which are stacked on one side of a surface of a first-conductive-type semiconductor substrate, wherein




a region of the second-conductive-type intermediate band gap layer other than its device center region is removed, and the second-conductive-type current diffusion layer is stacked in the removal region on the second-conductive-type second cladding layer,




the second-conductive-type current diffusion layer and the second-conductive-type second cladding layer have an energy band structure in which an upper-end position of valence band and a lower-end position of conduction band are in a type II relation, and wherein




the semiconductor light-emitting device further comprises a first electrode formed overall on the other side of the surface of the first-conductive-type semiconductor substrate, and a second electrode formed over the region other than the device center region on the second-conductive-type current diffusion layer.




With the semiconductor light-emitting device having this constitution, at the removal region where the region of the second-conductive-type intermediate band gap layer other than its device center region has been removed, the junction plane of the second-conductive-type current diffusion layer and the second-conductive-type second cladding layer having the energy band structure of the type II becomes high in resistance. Thus, the current flows to the device center region and, as a result, ineffective currents flowing under the second electrode formed over the region other than the device center region on the second-conductive-type current diffusion layer can be reduced, so that the emission intensity is enhanced.




In one embodiment of the present invention, an upper-side portion of the region of the second-conductive-type second cladding layer opposed to the removal region of the second-conductive-type intermediate band gap layer is removed.




With the semiconductor light-emitting device of this embodiment, both the removal region of the second-conductive-type intermediate band gap layer other than its device center region and the region where the upper-side portion of the second-conductive-type second cladding layer opposed to the removal region has been removed become high in resistance, and besides the high-resistance interface of the second-conductive-type current diffusion layer and the second-conductive-type second cladding layer is near the active layer. Thus, the ineffective currents flowing under the second electrode can further be reduced so that the emission intensity is further enhanced.




Also, there is provided a semiconductor light-emitting device comprising: a first-conductive-type first cladding layer, a first-conductive-type or second-conductive-type or an undoped active layer, a second-conductive-type second cladding layer, a second-conductive-type etching stop layer, a second-conductive-type third cladding layer, a second-conductive-type intermediate band gap layer and a second-conductive-type current diffusion layer, all of which are stacked on one side of a surface of a first-conductive-type semiconductor substrate, wherein




regions of the second-conductive-type intermediate band gap layer and the second-conductive-type third cladding layer other than their device center regions are removed, respectively, and the second-conductive-type current diffusion layer is stacked in the removal regions on the second-conductive-type etching stop layer,




the second-conductive-type current diffusion layer, the second-conductive-type etching stop layer and the second-conductive-type second cladding layer have an energy band structure in which an upper-end position of valence band and a lower-end position of conduction band are in a type II relation, and wherein




the semiconductor light-emitting device further comprises a first electrode formed overall on the one side of the surface of the first-conductive-type semiconductor substrate, and a second electrode formed over the region other than the device center region on the second-conductive-type current diffusion layer.




With the semiconductor light-emitting device of this constitution, the removal regions other than the device center regions where the regions of the second-conductive-type intermediate band gap layer and the second-conductive-type third cladding layer have been removed become high in resistance due to the fact that an energy band structure in which the upper-end position of the valence band and the lower-end position of the conduction band are in the type II relation is formed in the second-conductive-type current diffusion layer, etching stop layer and second cladding layer, and besides the high-resistance interface can be formed with high controllability near the active layer by the presence of the second-conductive-type etching stop layer. Thus, there can be fabricated a semiconductor light-emitting device less in ineffective currents and high in emission intensity with a good yield.




In one embodiment of the present invention, a protective layer of the second conductive type is formed on the second-conductive-type intermediate band gap layer.




With the semiconductor light-emitting device of this embodiment, since the second-conductive-type protective layer is present on the second-conductive-type intermediate band gap layer, there is no resistance layer of the interface with the current diffusion layer formed on the second-conductive-type protective layer. Thus, the operating voltage can be lowered.




In one embodiment of the present invention, the first-conductive-type semiconductor substrate is made of GaAs,




the first-conductive-type first cladding layer, the first-conductive-type or second-conductive-type or undoped active layer and the second-conductive-type second cladding layer are made of an AlGaInP-based compound semiconductor that provides lattice matching with GaAs,




the second-conductive-type current diffusion layer is made of a GaP- or AlGaInP-based compound semiconductor, and




the second-conductive-type intermediate band gap layer is made of an AlGaInP-based compound semiconductor.




With the semiconductor light-emitting device of this embodiment, ineffective currents can be reduced so that an AlGaInP-based semiconductor light-emitting device of high emission intensity can be realized.




In one embodiment of the present invention, the first-conductive-type semiconductor substrate is made of GaAs,




the first-conductive-type first cladding layer, the first-conductive-type or second-conductive-type or undoped active layer, the second-conductive-type second cladding layer, the second-conductive-type etching stop layer and the second-conductive-type third cladding layer are made of an AlGaInP-based compound semiconductor that provides lattice matching with GaAs,




the second-conductive-type current diffusion layer is made of a GaP- or AlGaInP-based compound semiconductor, and the second-conductive-type intermediate band gap layer is made of an AlGaInP-based compound semiconductor.




With the semiconductor light-emitting device of this embodiment, ineffective currents can be reduced with a simple construction so that an AlGaInP-based semiconductor light-emitting device of high emission intensity can be realized.




In one embodiment of the present invention, the second-conductive-type intermediate band gap layer made of the AlGaInP-based compound semiconductor has a rate Δa/a of lattice matching to GaAs falling within a range of −3.2%≦Δa/a≦−2.5%.




With the semiconductor light-emitting device of this embodiment, by the arrangement that the lattice matching rate Δa/a of the second-conductive-type intermediate band gap layer to GaAs is set to within a range of −3.2%≦Δa/a≦−2.5% in an AlGaInP-based semiconductor light-emitting device, ineffective currents can be reduced and the emission intensity can be enhanced, and besides, the operating voltage can be lowered. Also, lattice defects on the device surface can be lessened and the reliability can be improved.




In one embodiment of the present invention, the second-conductive-type intermediate band gap layer is composed of a plurality of AlGaInP layers having different rates of lattice matching to GaAs, the lattice matching rates Δa/a of those AlGaInP layers each falling within a range of −3.2≦Δa/a≦−2.5%.




With the semiconductor light-emitting device of this embodiment, the AlGaInP layers composing the second-conductive-type intermediate band gap layer are different from one another in the lattice matching rate and moreover the lattice matching rates Δa/a of those AlGaInP layers each fall within a range of −3.2≦Δa/a≦−2.5%. As a result, in the AlGaInP-based light-emitting device, ineffective currents can be reduced, by which the emission intensity can be enhanced, and besides the operating voltage can further be lowered and lattice defects on the device surface can be lessened.




In one embodiment of the present invention, a second-conductive-type protective layer made of GaP or an AlGaInP-based compound semiconductor having a Al composition ratio of not more than 20% relative to the total of III group is stacked on the second-conductive-type intermediate band gap layer.




With the semiconductor light-emitting device of this embodiment, since GaP or an AlGaInP protective layer containing less Al is present on the second-conductive-type intermediate band gap layer, there is no resistance layer with the second-conductive-type current diffusion layer formed on the AlGaInP protective layer, so that the operating voltage can be lowered.




In one embodiment of the present invention, the second-conductive-type second cladding layer and the second-conductive-type third cladding layer both made of an AlGaInP-based compound semiconductor have a composition of (Al


x


Ga


1−x


)


0.5


In


0.5


P (where 0.6≦x≦1.0).




With the semiconductor light-emitting device of this embodiment, the second-conductive-type second cladding layer and the second-conductive-type third cladding layer each have a composition of (Al


x


Ga


1−x


)


0.5


In


0.5


P (where 0.6≦x≦1.0). As a result of this, the operating voltage can be lowered.




In one embodiment of the present invention, the second-conductive-type intermediate band gap layer has a layer thickness of not more than 0.5 μm.




With the semiconductor light-emitting device of this embodiment, the second-conductive-type intermediate band gap layer has a layer thickness of not more than 0.5 μm. As a result of this, the operating voltage can be lowered.




In one embodiment of the present invention, the second-conductive-type intermediate band gap layer has a carrier concentration of not less than 0.5×10


18


cm


−3


.




With the semiconductor light-emitting device of this embodiment, the second-conductive-type intermediate band gap layer has a carrier concentration of not less than 0.5×10


18


cm


−3


. As a result of this, the operating voltage can be lowered.




Also, there is provided a method for manufacturing a semiconductor light-emitting device, comprising the steps of:




stacking, one by one on one side of a surface of a first-conductive-type semiconductor substrate, a first-conductive-type first cladding layer, a first-conductive-type or second-conductive-type or an undoped active layer, a second-conductive-type second cladding layer, a second-conductive-type intermediate band gap layer and a second-conductive-type protective layer;




removing a device center region of the second-conductive-type protective layer and a device center region of the second-conductive-type intermediate band gap layer, respectively, by etching;




after the removal step of the second-conductive-type protective layer and intermediate band gap layer, stacking a current diffusion layer on the second-conductive-type protective layer and the second-conductive-type second cladding layer to form, in the second-conductive-type current diffusion layer and the second-conductive-type second cladding layer, an energy band structure in which an upper-end position of valence band and a lower-end position of conduction band are in a type II relation;




forming a first electrode overall on the other side of the surface of the first-conductive-type semiconductor substrate; and




forming a second electrode over the device center region on the second-conductive-type current diffusion layer.




With this semiconductor light-emitting device manufacturing method, the removal region where the device center region of the second-conductive-type intermediate band gap layer has been removed becomes high in resistance because an energy band structure in which the upper-end position of the valence band and the lower-end position of the conduction band are in the type II relation is formed in the second-conductive-type current diffusion layer and second cladding layer become high in resistance. Thus, the current flows to around the removal region, so that ineffective currents flowing under the second electrode formed in the device center region on the second-conductive-type current diffusion layer can be reduced, allowing the emission intensity to be enhanced. Therefore, a semiconductor light-emitting device of high emission intensity can be manufactured.




Also, there is provided a method for manufacturing a semiconductor light-emitting device, comprising the steps of:




stacking, one by one on one side of a surface of a first-conductive-type semiconductor substrate, a first-conductive-type first cladding layer, a first-conductive-type or second-conductive-type or an undoped active layer, a second-conductive-type second cladding layer, a second-conductive-type intermediate band gap layer and a second-conductive-type protective layer;




removing a device center region of the second-conductive-type protective layer and a device center region of the second-conductive-type intermediate band gap layer, respectively, by etching, and further removing an upper-side portion of a region of the second-conductive-type second cladding layer corresponding to the removal region by etching;




after the removal step of the second-conductive-type protective layer, intermediate band gap layer and second cladding layer, stacking a second-conductive-type current diffusion layer on the second-conductive-type protective layer and the second-conductive-type second cladding layer to form, in the second-conductive-type current diffusion layer and the second-conductive-type second cladding layer, an energy band structure in which an upper-end position of valence band and a lower-end position of conduction band are in a type II relation;




forming a first electrode overall on the other side of the surface of the first-conductive-type semiconductor substrate; and




forming a second electrode over the device center region on the second-conductive-type current diffusion layer.




With this semiconductor light-emitting device manufacturing method, the removal region where the device center region of the second-conductive-type intermediate band gap layer has been removed becomes high in resistance because an energy band structure in which the upper-end position of the valence band and the lower-end position of the conduction band are in the type II relation is formed in the second-conductive-type current diffusion layer and second cladding layer become high in resistance. Thus, the current flows to around the removal region, so that ineffective currents flowing under the second electrode formed in the device center region on the second-conductive-type current diffusion layer can be reduced, allowing the emission intensity to be enhanced. Therefore, a semiconductor light-emitting device of high emission intensity can be manufactured.




Also, there is provided a method for manufacturing a semiconductor light-emitting device, comprising the steps of:




stacking, one by one on one side of a surface of a first-conductive-type semiconductor substrate, a first-conductive-type first cladding layer, a first-conductive-type or second-conductive-type or an undoped active layer, a second-conductive-type second cladding layer, a second-conductive-type etching stop layer, a second-conductive-type third cladding layer, a second-conductive-type intermediate band gap layer and a second-conductive-type protective layer;




removing device center regions of the second-conductive-type protective layer, the second-conductive-type intermediate band gap layer and the second-conductive-type third cladding layer by etching;




after the removal step of the second-conductive-type protective layer, intermediate band gap layer and third cladding layer, stacking a second-conductive-type current diffusion layer on the second-conductive-type protective layer and the second-conductive-type etching stop layer to form, in the second-conductive-type current diffusion layer, the second-conductive-type etching stop layer and the second-conductive-type second cladding layer, an energy band structure in which an upper-end position of valence band and a lower-end position of conduction band are in a type II relation;




forming a first electrode overall on the other side of the surface of the first-conductive-type semiconductor substrate; and




forming a second electrode over the device center region on the second-conductive-type current diffusion layer.




With this semiconductor light-emitting device manufacturing method, the removal region where the device center region of the second-conductive-type intermediate band gap layer has been removed becomes high in resistance because an energy band structure in which the upper-end position of the valence band and the lower-end position of the conduction band are in the type II relation is formed in the second-conductive-type current diffusion layer, the second-conductive-type eching stop layer and second cladding layer become high in resistance. Thus, the current flows to around the removal region, so that ineffective currents flowing under the second electrode formed in the device center region on the second-conductive-type current diffusion layer can be reduced, allowing the emission intensity to be enhanced. Therefore, a semiconductor light-emitting device of high emission intensity can be manufactured. Besides, the high-resistance interface can be formed with high controllability near the active layer by the presence of the second-conductive-type etching stop layer. Thus, the yield of this semiconductor light-emitting device can be improved.




Also, there is provided a method for manufacturing a semiconductor light-emitting device, comprising the steps of:




stacking, one by one on one side of a surface of a first-conductive-type semiconductor substrate, a first-conductive-type first cladding layer, a first-conductive-type or second-conductive-type or an undoped active layer, a second-conductive-type second cladding layer, a second-conductive-type intermediate band gap layer and a second-conductive-type protective layer;




removing regions of the second-conductive-type protective layer and the second-conductive-type intermediate band gap layer other than their device center regions, respectively, by etching;




after the removal step of the second-conductive-type protective layer and intermediate band gap layer, stacking a second-conductive-type current diffusion layer on the second-conductive-type protective layer and the second-conductive-type second cladding layer to form, in the second-conductive-type current diffusion layer and the second-conductive-type second cladding layer, an energy band structure in which an upper-end position of valence band and a lower-end position of conduction band are in a type II relation;




forming a first electrode overall on the other side of the surface of the first-conductive-type semiconductor substrate; and




forming a second electrode over the region other than the device center region on the second-conductive-type current diffusion layer.




With this semiconductor light-emitting device manufacturing method, the removal region where the region of the second-conductive-type intermediate band gap layer other than its device center region has been removed becomes high in resistance due to the fact that an energy band structure in which the upper-end position of the valence band and the lower-end position of the conduction band are in the type II relation is formed in the second-conductive-type current diffusion layer and second cladding layer. Thus, the current flows to around the device center region and, as a result, ineffective currents flowing under the second electrode formed over the region other than the device center region on the second-conductive-type current diffusion layer can be reduced, so that the emission intensity is enhanced. Therefore, a semiconductor light-emitting device of high emission intensity can be manufactured.




Also, there is provided a method for manufacturing a semiconductor light-emitting device, comprising the steps of:




stacking, one by one on one side of a surface of a first-conductive-type semiconductor substrate, a first-conductive-type first cladding layer, a first-conductive-type or second-conductive-type or an undoped active layer, a second-conductive-type second cladding layer, a second-conductive-type intermediate band gap layer and a second-conductive-type protective layer;




removing regions of the second-conductive-type protective layer and the second-conductive-type intermediate band gap layer other than their device center regions, respectively, by etching, and further removing an upper-side portion of a region of the second-conductive-type second cladding layer corresponding to the removal region by etching;




after the removal step of the second-conductive-type protective layer, intermediate band gap layer and second cladding layer, stacking a second-conductive-type current diffusion layer on the second-conductive-type protective layer and the second-conductive-type second cladding layer to form, in the second-conductive-type current diffusion layer and the second-conductive-type second cladding layer, an energy band structure in which an upper-end position of valence band and a lower-end position of conduction band are in a type II relation;




forming a first electrode overall on the other side of the surface of the first-conductive-type semiconductor substrate; and




forming a second electrode over the region other than the device center region on the second-conductive-type current diffusion layer.




With this semiconductor light-emitting device manufacturing method, the removal region where the region of the second-conductive-type intermediate band gap layer other than its device center region has been removed becomes high in resistance due to the fact that an energy band structure in which the upper-end position of the valence band and the lower-end position of the conduction band are in the type II relation is formed in the second-conductive-type current diffusion layer and second cladding layer. Thus, the current flows to around the device center region and, as a result, ineffective currents flowing under the second electrode formed over the region other than the device center region on the second-conductive-type current diffusion layer can be reduced, so that the emission intensity is enhanced. Therefore, a semiconductor light-emitting device of high emission intensity can be manufactured.




Also, there is provided a method for manufacturing a semiconductor light-emitting device, comprising the steps of:




stacking, one by one on one side of a surface of a first-conductive-type semiconductor substrate, a first-conductive-type first cladding layer, a first-conductive-type or second-conductive-type or an undoped active layer, a second-conductive-type second cladding layer, a second-conductive-type etching stop layer, a second-conductive-type third cladding layer, a second-conductive-type intermediate band gap layer and a second-conductive-type protective layer;




removing regions of the second-conductive-type protective layer, the second-conductive-type intermediate band gap layer and the second-conductive-type third cladding layer other than their device center regions, respectively, by etching;




after the removal step of the second-conductive-type protective layer, intermediate band gap layer and third cladding layer, stacking a second-conductive-type current diffusion layer on the second-conductive-type protective layer and the second-conductive-type etching stop layer to form, in the second-conductive-type current diffusion layer, the second-conductive-type etching stop layer and the second-conductive-type second cladding layer, an energy band structure in which an upper-end position of valence band and a lower-end position of conduction band are in a type II relation;




forming a first electrode overall on the other side of the surface of the first-conductive-type semiconductor substrate; and




forming a second electrode over the region other than the device center region on the second-conductive-type current diffusion layer.




With this semiconductor light-emitting device manufacturing method, the removal region where the region of the second-conductive-type intermediate band gap layer other than its device center region has been removed becomes high in resistance due to the fact that an energy band structure in which the upper-end position of the valence band and the lower-end position of the conduction band are in the type II relation is formed in the second-conductive-type current diffusion layer, the second-conductive-type eching stop layer and second cladding layer. Thus, the current flows to around the device center region and, as a result, ineffective currents flowing under the second electrode formed over the region other than the device center region on the second-conductive-type current diffusion layer can be reduced, so that the emission intensity is enhanced. Therefore, a semiconductor light-emitting device of high emission intensity can be manufactured.











BRIEF DESCRIPTION OF THE DRAWINGS




The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:





FIG. 1A

is a top view of a semiconductor light-emitting device which is a first embodiment of the invention,





FIG. 1B

is a sectional view of the semiconductor light-emitting device, and





FIG. 1C

is a functional view showing a current flow in the semiconductor light-emitting device;





FIGS. 2A

to


2


C are band junction diagrams for explaining the effects of the invention;





FIG. 3A

is a top view of a semiconductor light-emitting device which is a second embodiment of the invention,





FIG. 3B

is a sectional view of the semiconductor light-emitting device, and





FIG. 3C

is a functional view showing a current flow in the semiconductor light-emitting device;





FIG. 4A

is a top view of a semiconductor light-emitting device which is a third embodiment of the invention,





FIG. 4B

is a sectional view of the semiconductor light-emitting device, and





FIG. 4C

is a functional view showing a current flow in the semiconductor light-emitting device;





FIG. 5A

is a top view of a semiconductor light-emitting device which is a fourth embodiment of the invention,





FIG. 5B

is a sectional view of the semiconductor light-emitting device, and





FIG. 5C

is a functional view showing a current flow in the semiconductor light-emitting device;





FIG. 6A

is a top view of a semiconductor light-emitting device which is a fifth embodiment of the invention,





FIG. 6B

is a sectional view of the semiconductor light-emitting device, and





FIG. 6C

is a functional view showing a current flow in the semiconductor light-emitting device;





FIG. 7A

is a top view of a semiconductor light-emitting device which is a sixth embodiment of the invention,





FIG. 7B

is a sectional view of the semiconductor light-emitting device, and





FIG. 7C

is a functional view showing a current flow in the semiconductor light-emitting device;





FIG. 8A

is a top view of a semiconductor light-emitting device which is a seventh embodiment of the invention, and





FIG. 8B

is a sectional view of the semiconductor light-emitting device;





FIG. 9A

is a top view of a semiconductor light-emitting device which is an eighth embodiment of the invention,





FIG. 9B

is a sectional view of the semiconductor light-emitting device, and





FIG. 9C

is a functional view showing a current flow in the semiconductor light-emitting device;





FIG. 10

is a chart showing variations in emission intensity versus the difference in diameter between electrode and current blocking (removal) region in the semiconductor light-emitting device;





FIG. 11

is a chart showing the relationship between mismatch of the intermediate band gap layer and operating voltage in the semiconductor light-emitting device;





FIG. 12

is a chart showing the relationship between mismatch of the intermediate band gap layer and the number of lattice defects in the semiconductor light-emitting device;





FIG. 13A

is a top view of a semiconductor light-emitting device which is a ninth embodiment of the invention, and





FIG. 13B

is a sectional view of the semiconductor light-emitting device;





FIG. 14

is a band junction diagram for explaining the effects of the semiconductor light-emitting device;





FIG. 15

is a chart showing the relationship between Al composition ratio of a protective layer and operating voltage in a semiconductor light-emitting device which is a tenth embodiment of the invention;





FIG. 16

is a chart showing the relationship between Al composition ratio of a p-cladding layer and operating voltage in a semiconductor light-emitting device which is an eleventh embodiment of the invention;





FIG. 17

is a chart showing the relationship between layer thickness of the intermediate band gap layer and operating voltage in the semiconductor light-emitting device;





FIG. 18

is a chart showing the relationship between carrier concentration of the intermediate band gap layer and operating voltage in the semiconductor light-emitting device;





FIGS. 19A-19D

are views showing a semiconductor light-emitting device manufacturing method which is a twelfth embodiment of the invention;





FIGS. 20A-20D

are views showing a semiconductor light-emitting device manufacturing method which is a thirteenth embodiment of the invention;





FIGS. 21A-21D

are views showing a semiconductor light-emitting device manufacturing method which is a fourteenth embodiment of the invention;





FIGS. 22A-22D

are views showing a semiconductor light-emitting device manufacturing method which is a fifteenth embodiment of the invention;





FIGS. 23A-23D

are views showing a semiconductor light-emitting device manufacturing method which is a sixteenth embodiment of the invention;





FIGS. 24A-24D

are views showing a semiconductor light-emitting device manufacturing method which is a seventeenth embodiment of the invention;





FIG. 25A

is a top view of a semiconductor light-emitting device according to the prior art,





FIG. 25B

is a sectional view of the semiconductor light-emitting device, and





FIG. 25C

is a functional view showing a current flow in the semiconductor light-emitting device;





FIG. 26A

is a top view of another semiconductor light-emitting device according to the prior art,





FIG. 26B

is a sectional view of the semiconductor light-emitting device, and





FIG. 26C

is a functional view showing a current flow in the semiconductor light-emitting device; and





FIG. 27A

is a top view of still another semiconductor light-emitting device according to the prior art,





FIG. 27B

is a sectional view of the semiconductor light-emitting device, and





FIG. 27C

is a functional view showing a current flow in the semiconductor light-emitting device.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS




Hereinbelow, the semiconductor light-emitting device and method of manufacture thereof according to the present invention are described in detail by way of embodiments thereof illustrated in the accompanying drawings.




(First Embodiment)





FIGS. 1A

,


1


B and


1


C are a top view, a sectional view, and a functional view showing a current flow, respectively, of a semiconductor light-emitting device which is a first embodiment of the invention.




In this semiconductor light-emitting device, as shown in

FIG. 1B

, an n-GaAs buffer layer


1


(thickness: 0.5 μm, Si doping: 5×10


17


cm


−3


), an n-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P first cladding layer


2


(thickness: 1.0 μm, Si doping:


5×l0




17


cm


−3


) , an undoped (Al


0.3


Ga


0.7


)


0.5


In


0.5


P active layer


3


(thickness: 0.6 μm), a p-(Al


0.7


Ga


0.3


l )


0.5


In


0.5


P second cladding layer


4


(thickness: 0.7 μm, Zn doping: 5×10


17


cm


−3


), a p-(Al


0.4


Ga


0.6


)


0.9


In


0.1


P intermediate band gap layer


5


(thickness: 0.15 μm, Zn doping: 2×10


18


cm


−3


), and a p-GaP current diffusion layer


6


(thickness: 6 μm, Zn doping: 2×10


18


cm


−3


) are stacked one by one on an n-GaAs substrate


10


by MOCVD process.




In this case, a device center region of the pAlGaInP intermediate band gap layer


5


is removed in a circular shape (the diameter of this circular-shaped removal region is 100 μm). Then, a first electrode


11


is formed on the substrate side while a circular-shaped second electrode


12


having a diameter of 100 μm is formed on the grown layer side (shown in FIG.


1


A). It is noted that the p-AlGaInP intermediate band gap layer


5


has a Δa/a=−2.8% mismatch in lattice matching ratio with respect to the nGaAs substrate


10


.




In this semiconductor light-emitting device, as shown in

FIG. 1C

, a current injected from the grown-layer side second electrode


12


avoids the region at which the p-AlGaInP intermediate band gap layer


5


provided under the second electrode


12


has been removed (removal region), flowing to around the removal region. Thus, light emission occurs over a region of the active layer


3


corresponding to the region other than the removal region (under the second electrode


12


). The reason of this is described below.




The p-AlGaInP second cladding layer


4


and the p-GaP current diffusion layer


6


are so positioned as to have such a positional relation of their conduction band lower ends and the valence band upper ends with respect to the vacuum level as shown in FIG.


2


A. When a heterojunction is formed in this case, there results a junction state of so-called type-II energy band structure which involves an increased band discontinuity of valence band.




Therefore, as an interface between the p-AlGaInP second cladding layer


4


and the p-GaP current diffusion layer


6


is present in the removal region under the second electrode


12


, the band junction state at the interface is as shown in

FIG. 2B

, where the notch of the valence band at the junction becomes large, causing a high resistance, to the current (holes) injected from the second electrode


12


on the grown layer side (where the notch height is about 0.28 eV).




Meanwhile, in the region other than the removal region (under the second electrode


12


), the layer structure is given by the p-AlGaInP second cladding layer


4


, the p-AlGaInP intermediate band gap layer


5


and the p-GaP current diffusion layer


6


, where the band junction state is as shown in

FIG. 2C

due to the presence of the p-AlGaInP intermediate band gap layer


5


. In this case, the band discontinuity is divided with the results of smaller notch of valence band at the junction, causing a low resistance (where the notch is divided into 0.15 eV and 0.13 eV).




Under operation as a device, in the case of a device made up only of the interface between the p-AlGaInP second cladding layer


4


and the p-GaP current diffusion layer


6


, as in the removal region under the second electrode


12


, the voltage at a 20 mA conduction is about 3.5 V because of a large notch height. Meanwhile, in the case of a semiconductor light-emitting device having the p-AlGaInP intermediate band gap layer


5


device, as in the region other than the removal region (under the second electrode


12


), the voltage at a 20 mA conduction is about 2.1 V, hence a voltage difference being as much as 1.4 V.




As a result, at a 20 mA conduction, as shown in

FIG. 1C

, a current injected from the grown-layer side second electrode


12


avoids the removal region under the second electrode


12


, flowing to around the region, causing light emission to occur over a region of the active layer


3


corresponding to the region other than the removal region (under the second electrode


12


).




In the case of this semiconductor light-emitting device, as in the semiconductor light-emitting device shown in

FIG. 26

, there occurs no sneak current to under the current blocking layer, so that ineffective currents are almost completely eliminated, resulting in increased emission intensity.




When this semiconductor light-emitting device of the first embodiment was applied to a 5 mm dia. molded article, the emission intensity at a 20 mA conduction was 3.0 cd, 1.5 times higher than that of the semiconductor light-emitting device shown in FIG.


26


.




(Second Embodiment)





FIGS. 3A

,


3


B and


3


C are a top view, a sectional view and a functional view, respectively, of a semiconductor light-emitting device which is a second embodiment of the invention.




In this semiconductor light-emitting device, as shown in

FIG. 3B

, an n-GaAs buffer layer


21


(thickness: 0.5 μm, Si doping: 5×10


17


cm


−3


), an n-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P first cladding layer


22


(thickness: 1.0 μm, Si doping: 5×10


17


cm


−3


), an undoped (Al


0.3


Ga


0.7


)


0.5


In


0.5


P active layer


23


(thickness: 0.6 μm), a p-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P second cladding layer


24


(thickness: 0.7 μm, Zn doping: 5×10


17


cm


−3


), a p-(Al


0.4


Ga


0.6


)


0.9


In


0.1


P intermediate band gap layer


25


(thickness: 0.15 μm, Zn doping: 2×10


18


cm


−3


), and a p-GaP current diffusion layer


26


(thickness: 6 μm, Zn doping: 2×10


18


cm


−3


) are stacked one by one on an n-GaAs substrate


30


by MOCVD process.




In this case, a device center region of the p-AlGaInP intermediate band gap layer


25


is removed in a circular shape, and a region of the p-AlGaInP second cladding layer


24


corresponding to the removal region is removed halfway on the upper side (remaining thickness: 0.3 μm) (the diameter of this circular shape is 100 μm). Then, a first electrode


31


is formed on the substrate side while a circular-shaped second electrode


32


having a diameter of 100 μm is formed on the grown layer side.




In this semiconductor light-emitting device, according to the same principle as in the semiconductor light-emitting device of the first embodiment, as shown in

FIG. 3C

, a current injected from the grown-layer side second electrode


32


avoids the removal region under the second electrode


32


, flowing to around the removal region. Thus, light emission occurs over a region of the active layer


23


corresponding to the region other than the removal region (under the second electrode


32


).




In the case of this semiconductor light-emitting device, as compared with the semiconductor light-emitting device of the first embodiment, the high-resistance interface formed by the p-AlGaInP second cladding layer


24


and the p-GaP current diffusion layer


26


under the second electrode


32


is just above the active layer


23


as near as 0.3 μm thereto, so that ineffective currents are lessened, resulting in further increased emission intensity.




When this semiconductor light-emitting device of the second embodiment was applied to a 5 mm dia. molded article, the emission intensity at a 20 mA conduction (operating voltage: 2.1 V) was 3.3 cd, showing a 10% increase as compared with the semiconductor light-emitting device of the first embodiment.




(Third Embodiment)





FIGS. 4A

,


4


B and


4


C are a top view, a sectional view and a functional view, respectively, of a semiconductor light-emitting device which is a third embodiment of the invention. In this semiconductor light-emitting device, as shown in

FIGS. 4A and 4B

, an n-GaAs buffer layer


41


(thickness: 0.5 μm, Si doping: 5×10


17


cm


−3


), an n-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P first cladding layer


42


(thickness: 1.0 μm, Si doping: 5×10


17


cm


−3


), an undoped (Al


0.3


Ga


0.7


)


0.5


In


0.5


P active layer


43


(thickness: 0.6 μm), a p-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P second cladding layer


44


(thickness: 0.3 μm), a p-GaInP etching stop layer


45


(thickness: 0.01 μm, Zn doping: 5×10


17


cm


−3


), a p-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P third cladding layer


46


(thickness: 0.4 μm, Zn doping: 5×10


17


cm


−3


), a p-(Al


0.4


Ga


0.6


)


0.9


In


0.1


P intermediate band gap layer


47


(thickness: 0.15 μm, Zn doping: 2×10


18


cm


−3


), and a p-GaP current diffusion layer


48


(thickness: 6 μm, Zn doping: 2×10


18


cm


−3


) are stacked one by one on an n-GaAs substrate


50


by MOCVD process.




In this case, device center regions of the p-AlGaInP intermediate band gap layer


47


and the p-AlGaInP third cladding layer


46


are removed in a circular shape (the diameter of these circular-shaped removal regions is 100 μm). Then, a first electrode


51


is formed on the substrate side while a circular-shaped second electrode


52


having a diameter of 100 μm is formed on the grown layer side.




In this semiconductor light-emitting device also, as shown in

FIG. 4C

, a current injected from the grownlayer side second electrode


52


avoids the removal region under the second electrode


52


, flowing to around the removal region. Thus, light emission occurs over a region of the active layer


43


corresponding to the region other than the removal region (under the second electrode


52


).




As to the reason of this, also at the interface between the p-GaInP etching stop layer


45


and the p-GaP current diffusion layer


48


present in the etched region under the second electrode


52


, the band junction state is one similar to

FIG. 2B

, where the notch at the junction becomes large, causing a high resistance, to the current (holes) injected from the second electrode


52


on the grown layer side (where the notch height is about 0.26 eV and the voltage at a 20 mA conduction is as large as 3.3 V).




This semiconductor light-emitting device of the third embodiment has effects similar to those of the semiconductor light-emitting device of the second embodiment, and further has better controllability in forming, at a position 0.3 μm just above the active layer


43


, the high-resistance interface formed by the p-AlGaInP second cladding layer


44


and the p-GaP current diffusion layer


48


under the second electrode


52


, as compared with the semiconductor light-emitting device of the second embodiment, by virtue of the use of the p-GaInP etching stop layer


45


. Thus, the yield of this semiconductor light-emitting device is improved.




With this semiconductor light-emitting device of the third embodiment, the emission intensity at a 20 mA conduction (operating voltage: 2.1 V) was 3.3 cd, the same as in the semiconductor light-emitting device of the second embodiment, while the yield was improved to 99% in contrast to 75% of the second embodiment.




(Fourth Embodiment)





FIGS. 5A

,


5


B and


5


C are a top view, a sectional view and a functional view, respectively, of a semiconductor light-emitting device which is a fourth embodiment of the invention.




In this semiconductor light-emitting device, as shown in

FIGS. 5A and 5B

, an n-GaAs buffer layer


61


(thickness: 0.5 μm, Si doping: 5×10


17


cm


−3


), a DBR (optical reflection) layer


62


formed of ten pairs of n-Al


0.5


In


0.5


P layer and n-(Al


0.4


Ga


0.6


)


0.5


In


0.5


P layer (each one layer's thickness: 0.05 μm, Si doping: 5×10


17


cm


−3


), an n-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P first cladding layer


63


(thickness: 1.0 μm, Si doping: 5×10


17


cm


−3


), a p-(Al


0.3


Ga


0.7


)


0.5


In


0.5


P active layer


64


(thickness: 0.6 μm, Zn doping: 2×10


17


cm


−3


), a p-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P second cladding layer


65


(thickness: 0.7 μm, Zn doping: 5×10


17


cm


−3


), a p-(Al


0.4


Ga


0.6


)


0.9


In


0.1


P intermediate band gap layer


66


(thickness: 0.15 μm, Zn doping: 2×10


18


cm


−3


), and a p-(Al


0.05


Ga


0.95


)


0.9


In


0.1


P current diffusion layer


67


(thickness: 6 μm, Zn doping: 3×10


18


cm


−3


) are stacked one by one on an n-GaAs substrate


70


by MOCVD process.




In this case, peripheries of the p-AlGaInP intermediate band gap layer


66


are removed with its device center region left in a circular shape (the diameter of this circular shape is 100 μm). Then, a first electrode


71


is formed on the substrate side while a second electrode


72


is formed on the grown layer side over a region other than a 100 μm dia. circular-shaped region which is left as it is.




A heterojunction of type II is formed also between the p-(Al


0.05


Ga


0.95


)


0.9


In


0.1


P current diffusion layer


67


and the p-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P second cladding layer


65


, and a high-resistance interface is formed at the removal region of the intermediate band gap layer


66


.




In the case of this semiconductor light-emitting device, as shown in

FIG. 5C

, a current injected from the grown-layer side second electrode


72


avoids the removal region under the second electrode


72


, flowing to the device center region. Thus, light emission occurs over a region of the active layer


64


corresponding to the region other than the removal region (under the second electrode


72


).




As a structure to be compared with this semiconductor light-emitting device, there has been a semiconductor light-emitting device having a structure shown in

FIGS. 27A-27C

similar to the prior-art semiconductor light-emitting device shown in FIG.


26


. In this semiconductor light-emitting device shown in

FIGS. 27A-27C

, as in the semiconductor light-emitting device shown in

FIG. 26

, most part of the current sneaks to under the second electrode on the under side of the current blocking layer, resulting in ineffective current, with lower light intensity (4 cd at a 20 mA conduction with a radiation angle of ±2°). As compared with this semiconductor light-emitting device shown in

FIGS. 27A-27C

, the semiconductor light-emitting device of this fourth embodiment involves less sneak current going to under the removal region, so that ineffective currents are almost completely eliminated, resulting in increased emission intensity.




With this semiconductor light-emitting device of the fourth embodiment, the emission intensity at a 20 mA conduction was 6.0 cd, 1.5 times higher than that of the semiconductor light-emitting device shown in

FIG. 27

, where the operating voltage was 2.35 V (because of a small current injection area, the operating voltage is larger than in the semiconductor light-emitting device shown in FIG.


25


).




(Fifth Embodiment)





FIGS. 6A

,


6


B and


6


C are a top view, a sectional view and a functional view, respectively, of a semiconductor light-emitting device which is a fifth embodiment of the invention.




In this semiconductor light-emitting device, as shown in

FIGS. 6A and 6B

, an n-GaAs buffer layer


81


(thickness: 0.5 μm, Si doping: 5×10


17


cm


−3


), a DBR (optical reflection) layer


82


formed of ten pairs of n-Al


0.5


In


0.5


P layer and n-(Al


0.4


Ga


0.6


)


0.5


In


0.5


P layer (each one layer's thickness: 0.05 μm, Si doping: 5×10


17


cm


−3


), an n-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P first cladding layer


83


(thickness: 1.0 μm, Si doping: 5×10


17


cm


−3


), a p-(Al


0.3


Ga


0.7


)


0.5


In


0.5


P active layer


84


(thickness: 0.6 μm, Zn doping: 2×10


17


cm


−3


), a p-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P second cladding layer


85


(thickness: 0.7 μm, Zn doping: 5×10


17


cm


−3


), a p-(Al


0.4


Ga


0.6


)


0.9


In


0.1


P intermediate band gap layer


86


(thickness: 0.15 μm, Zn doping: 2×10


18


cm


−3


), and a p-(Al


0.05


Ga


0.95


)


0.9


In


0.1


P current diffusion layer


87


(thickness: 6 μm, Zn doping: 3×10


18


cm


−3


)are stacked one by one on an n-GaAs substrate


90


by MOCVD process.




In this case, peripheries of the p-AlGaInP intermediate band gap layer


86


are removed with its device center region left in a circular shape, and a region of the p-AlGaInP second cladding layer


85


corresponding to the removal region is removed halfway on the upper side (remaining thickness: 0.3 μm) (the diameter of this circular shape is 100 μm). Then, a first electrode


91


is formed on the substrate side while a second electrode


92


is formed on the grown layer side over a region other than a 100 μm dia. circular-shaped region which is left as it is.




In the case of this semiconductor light-emitting device, as shown in

FIG. 6C

, a current injected from the grown-layer side second electrode


92


avoids the removal region under the second electrode


92


, flowing to the device center region. Thus, light emission occurs over a region of the active layer


84


corresponding to the region other than the removal region (under the second electrode


92


).




This semiconductor light-emitting device of the fifth embodiment has effects similar to those of the semiconductor light-emitting device of the fourth embodiment, and further, as compared with the semiconductor light-emitting device of the fourth embodiment, the high-resistance interface formed by the p-AlGaInP second cladding layer


85


and the p-AlGaInP current diffusion layer


87


under the second electrode


92


is just above the active layer


84


as near as 0.3 μm thereto, so that ineffective currents are lessened, resulting in further increased emission intensity. The emission intensity at a 20 mA conduction (operating voltage: 2.35 V) was 6.6 cd, showing a 10% increase as compared with the semiconductor light-emitting device of the first embodiment.




(Sixth Embodiment)





FIGS. 7A

,


7


B and


7


C are a top view, a sectional view and a functional view, respectively, of a semiconductor light-emitting device which is a sixth embodiment of the invention.




In this semiconductor light-emitting device, as shown in

FIGS. 7A and 7B

, an n-GaAs buffer layer


101


(thickness: 0.5 μm, Si doping: 5×10


17


cm


−3


), a DBR (optical reflection) layer


102


formed of ten pairs of n-Al


0.5


In


0.5


P layer and n-(Al


0.4


Ga


0.6


)


0.5


In


0.5


P layer (each one layer's thickness: 0.05 μm, Si doping: 5×10


17


cm


−3


), an n-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P first cladding layer


103


(thickness: 1.0 μm, Si doping: 5×10


17


cm


−3


), a p-(Al


0.3


Ga


0.7


)


0.5


In


0.5


P active layer


104


(thickness: 0.6 μm, Zn doping: 2×10


17


cm


−3


), a p-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P second cladding layer


105


(thickness: 0.3, Zn doping: 5×10


17


cm


−3


), a p-Ga


0.5


In


0.5


P etching stop layer


106


(thickness: 0.01 μm, Zn doping: 5×10


17


cm


−3


), a p-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P third cladding layer


107


(thickness: 0.4 μm, Zn doping: 5×10


17


cm


−3


) a p-(Al


0.4


Ga


0.6


)


0.9


In


0.1


P intermediate band gap layer


108


(thickness: 0.15 μm, Zn doping: 2×10


18


cm


−3


), and a p-(Al


0.05


Ga


0.95


)


0.9


In


0.1


P current diffusion layer


109


(thickness: 6 μm, Zn doping: 3×10


18


cm


−3


) are stacked one by one on an n-GaAs substrate


110


by MOCVD process.




In this case, peripheries of the p-AlGaInP intermediate band gap layer


108


are removed with its device center region left in a circular shape, and a region of the p-AlGaInP third cladding layer


107


corresponding to the removal region is removed (the diameter of this circular shape is 100 μm) . Then, a first electrode


111


is formed on the substrate side while a second electrode


112


is formed on the grown layer side over a region other than a 100 μm dia. circular-shaped region which is left as it is.




In the case of this semiconductor light-emitting device, as shown in

FIG. 7C

, a current injected from the grown-layer side second electrode


112


avoids the removal region under the second electrode


112


, flowing to the device center region. Thus, light emission occurs over a region of the active layer


104


corresponding to the region other than the removal region (under the second electrode


112


).




This semiconductor light-emitting device of the sixth embodiment has effects similar to those of the semiconductor light-emitting device of the fifth embodiment, and further, has better controllability in forming, at a position 0.3 μm just above the active layer


104


, the high-resistance interface formed by the p-AlGaInP third cladding layer


107


and the p-AlGaInP current diffusion layer


109


under the second electrode


112


, as compared with the semiconductor light-emitting device of the fifth embodiment, by virtue of the use of the etching stop layer


106


. Thus, the yield of this semiconductor light-emitting device is improved.




With this semiconductor light-emitting device of the sixth embodiment, the emission intensity at a 20 mA conduction (operating voltage: 2.35 V) was 6.6 cd, the same as in the semiconductor light-emitting device of the fifth embodiment, while the yield was improved to 99% (against 75% of the semiconductor light-emitting device of the fifth embodiment).




(Seventh Embodiment)





FIGS. 8A and 8B

are a top view and a sectional view, respectively, of a semiconductor light-emitting device which is a seventh embodiment of the invention.




In this semiconductor light-emitting device, as shown in

FIGS. 8A and 8B

, an n-GaAs buffer layer


121


(thickness: 0.5 μm, Si doping: 5×10


17


cm


−3


), an n-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P first cladding layer


122


(thickness: 1.0 μm, Si doping: 5×10


−3


), an undoped (Al


0.3


Ga


0.7


)


0.5


In


0.5


P active layer


123


(thickness: 0.6 μm), a p-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P second cladding layer


124


(thickness: 0.7 μm, Zn doping: 5×10


17


cm


−3


), a p-(Al


0.4


Ga


0.6


)


0.9


In


0.1


P intermediate band gap layer


125


(thickness: 0.15 μm, Zn doping: 2×10


18


cm


−3


), a p-GaP protective layer


126


(thickness: 0.1 μm, Zn doping: 1×10


18


cm


−3


), and a p-GaP current diffusion layer


127


(thickness: 6 μm, Zn doping: 2×10


18


cm


−3


) are stacked one by one on an n-GaAs substrate


130


by MOCVD process.




In this case, device center regions of the p-GaP protective layer


126


and the p-AlGaInP intermediate band gap layer


125


are removed in a circular shape (the diameter of these circular-shaped removal regions is 100 μm). Then, a first electrode


131


is formed on the substrate side while a second electrode


132


having a diameter of 100 μm is formed on the grown layer side over a region opposite to the removal region (shown in FIG.


8


A).




This semiconductor light-emitting device of the seventh embodiment differs from the semiconductor light-emitting device of the first embodiment shown in

FIG. 1

in that the p-GaP protective layer


126


is present on the p-AlGaInP intermediate band gap layer


125


.




In the case of this semiconductor light-emitting device, a current injected from the grown-layer side second electrode


132


avoids the regions at which the p-GaP protective layer


126


and the p-AlGaInP intermediate band gap layer


125


provided under the second electrode


132


have been removed, flowing to around the removal region. Thus, light emission occurs over a region of the active layer


123


corresponding to the region other than the removal region (under the second electrode


132


).




With this semiconductor light-emitting device, the operating voltage at 20 mA was 2.0 V, which was a decrease of 0.1 V as compared with the semiconductor light-emitting device of the first embodiment. This is because whereas the ground of the regrown interface in the region through which the current flows in the case of the semiconductor light-emitting device of the first embodiment is given by the p-AlGaInP intermediate band gap layer


125


, which is a layer containing much Al (36% on the basis of a total of III group), the counterpart in the case of this semiconductor light-emitting device of the seventh embodiment is given by the p-GaP protective layer


126


, which is a layer containing no Al, so that there occurs no resistive layer due to any Al oxide at the interface.




When this semiconductor light-emitting device of the seventh embodiment was applied to a 5 mm dia. molded article, the emission intensity at a 20 mA conduction was 3.0 cd, the same as in the semiconductor light-emitting device of the first embodiment.




(Eighth Embodiment)





FIGS. 9A

,


9


B and


9


C are a top view, a sectional view and a functional view, respectively, of a semiconductor light-emitting device which is an eighth embodiment of the invention.




In this semiconductor light-emitting device, as shown in

FIGS. 9A and 9B

, an n-GaAs buffer layer


141


(thickness: 0.5 μm, Si doping: 5×10


17


cm


−3


), an n-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P first cladding layer


142


(thickness: 1.0 μm, Si doping: 5×10


17


cm


−3


), an undoped (Al


0.3


Ga


0.7


)


0.5


In


0.5


P active layer


143


(thickness: 0.6 μm), a p-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P second cladding layer


144


(thickness: 0.7, Zn doping: 5×10


17


cm


−3


), a p-(Al


0.4


Ga


0.6


)


0.9


In


0.1


P intermediate band gap layer


145


(thickness: 0.15 μm, Zn doping: 2×10


18


cm


−3


), a p-GaP protective layer


146


(thickness: 0.1 μn, Zn doping: 1×10


18


cm


−3


), and a p-GaP current diffusion layer


147


(thickness: 6 μm, Zn doping: 2×10


18


cm


−3


) are stacked one by one on an n-GaAs substrate


150


by MOCVD process.




In this case, device center regions of the p-GaP protective layer


146


and the p-AlGaInP intermediate band gap layer


145


are removed in a circular shape (the diameter of these circular-shaped removal regions


153


is 100 μm). Then, a first electrode


151


is formed on the substrate side while a second electrode


152


is formed on the grown layer side over a region opposite to the removal region.




This semiconductor light-emitting device of the eighth embodiment has a 80 μm diameter of the grown-layer side second electrode


152


, 20 μm smaller than that of the semiconductor light-emitting device of the seventh embodiment shown in

FIG. 8

(the electrode diameter in the first embodiment is 100 μm).




In the case of this semiconductor light-emitting device, as shown in

FIG. 9C

, a current injected from the grown-layer side second electrode


152


avoids the removal region present under the second electrode


152


, flowing to around the removal region. Thus, light emission occurs over a region of the active layer


143


corresponding to the region other than the removal region (under the second electrode


152


). However, since there is a positional shift of 10 μm between the end of the second electrode


152


and the end of the removal region (center region), the current spreading becomes slightly worse than in the seventh embodiment (in which the electrode end and the removal region end are coincident).




With this semiconductor light-emitting device of the eighth embodiment, the emission intensity at a 20 mA conduction was 2.7 cd, which is 90% that of the semiconductor light-emitting device shown in the seventh embodiment shown in FIG.


8


.





FIG. 10

shows the relationship of the light intensity of the eighth embodiment device to the difference between electrode diameter (the diameter of the second electrode


152


) and current blocking region diameter (the diameter of the removal region). In

FIG. 10

, the minus sign represents that the electrode diameter is smaller than the current blocking region diameter, and the plus sign represents that it is larger, conversely.




As can be understood from

FIG. 10

, in the case where the electrode diameter is larger than the current blocking region diameter converse to the semiconductor light-emitting device of the eighth embodiment, there is formed a light emitting region under the electrode, causing the light intensity to become smaller.




If the difference between the electrode diameter and the current blocking region diameter is within ±40 μm, then the resulting light intensity is 80% or more that in the case where the two diameters are equal to each other.




Also,

FIG. 11

shows the 20 mA operating voltage of the eighth embodiment resulting when the mismatch (in composition) of the intermediate band gap layer


145


is varied. The operating voltage increases as the mismatch becomes smaller than −2.8% (meaning that the composition approaches GaP). This is because, with reference to the band junction diagram shown by

FIG. 2C

, the notch of the valence band at the interface of the p-AlGaInP cladding layer and the p-AlGaInP intermediate layer increases. Desirably, the mismatch of the intermediate band gap is not less than −3.2% in order that the operating voltage is not more than 2.5 V, which is practically free from any problems.




Also,

FIG. 12

shows the number of defects (per mm


2


) at the crystal surface of the first embodiment resulting when the mismatch (in composition) of the intermediate band gap layer is varied. The crystal defects increase as the mismatch becomes larger than −2.8% (meaning that the In composition increases) . This is because, at a mismatched layer such as the intermediate layer, In hardly migrates but tends to anisotropically grow because of some stress. Desirably, the mismatch of the intermediate band gap is not more than −2.5% in order that the number of defects is not more than 20, which is practically free from any problems.




(Ninth Embodiment)





FIGS. 13A and 13B

are a top view and a sectional view, respectively, of a semiconductor light-emitting device which is a ninth embodiment of the invention.




In this semiconductor light-emitting device, as shown in

FIGS. 13A and 13B

, an n-GaAs buffer layer


161


(thickness: 0.5 μm, Si doping: 5×10


17


cm


−3


), an n-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P first cladding layer


162


(thickness: 1.0 μm, Si doping: 5×10


17


cm


−3


an undoped (Al


0.3


Ga


0.7


)


0.5


In


0.5


P active layer


163


(thickness: 0.6 μm), a p-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P second cladding layer


164


(thickness: 0.7 μm, Zn doping: 5×10


17


cm


−3


), a p-AlGaInP intermediate band gap layer


165


(thickness: 0.15 μm. Zn doping: 2×10


18


cm


−3


), a p-GaP protective layer


166


(thickness: 0.1 μm, Zn doping: 1×10


18


cm


−3


), and a p-GaP current diffusion layer


167


(thickness: 6 μm, Zn doping: 2×10


18


cm


−3


) are stacked one by one on an n-GaAs substrate


170


by MOCVD process.




In this case, device center regions of the p-GaP protective layer


166


and the p-AlGaInP intermediate band gap layer


165


are removed in a circular shape (the diameter of these circular-shaped removal regions is 100 μm). Then, a first electrode


171


is formed on the substrate side while a second electrode


172


having a diameter of 100 μm is formed on the grown layer side over a region opposite to the removal region.




This semiconductor light-emitting device of the ninth embodiment differs from the semiconductor light-emitting device of the seventh embodiment shown in

FIG. 8

in that the intermediate band gap layer


165


is formed of three layers. More specifically, the intermediate band gap layer


165


is formed of a first intermediate band gap layer


165


A having a mismatch of −2.6% (thickness: 0.5 μm, Zn doping: 1×10


18


cm


−3


), a second intermediate band gap layer


165


B having a mismatch of −2.8% (thickness: 0.05 μm, Zn doping: 1×10


18


cm


−3


), and a third intermediate band gap layer


165


C having a mismatch of −3.0% (thickness: 0.05 μm, Zn doping: 1×10


18


cm


−3


), in this order from below.




With this semiconductor light-emitting device of the ninth embodiment, the operating voltage at 20 mA was 1.90 V, smaller as compared with the semiconductor light-emitting device of the seventh embodiment. The reason of this is that, as can be understood from the band junction diagram shown in

FIG. 14

, the notch height at the junction is further divided and decreased.




Although the ninth embodiment has been described with respect to a semiconductor light-emitting device in which the number of intermediate band gap layers are has been set to 3 layers, yet the number of intermediate band gap layers may be an arbitrary number (2 layers or more).




(Tenth Embodiment)




The semiconductor light-emitting device of a tenth embodiment of the invention differs from the semiconductor light-emitting device of the seventh embodiment in that the second-conductive-type protective layer is a p-Al


0.05


Ga


0.9


In


0.05


P layer.




In this semiconductor light-emitting device of the tenth embodiment, although the ground of the regrown interface in the region through which the current flows is given by a layer containing Al, the 20 mA operating voltage is 2.0 V because the Al content as small as 5% on the basis of a total of the III group. The resulting operating voltage is the same as in the semiconductor light-emitting device of the seventh embodiment.




When this semiconductor light-emitting device of the tenth embodiment was applied to a 5 mm dia. molded article, the emission intensity at a 20 mA conduction was 3.0 cd, the same as in the semiconductor light-emitting device of the first embodiment.





FIG. 15

shows the 20 mA operating voltage of the semiconductor light-emitting device of the seventh embodiment resulting when the Al composition ratio of the second-conductive-type AlGaInP protective layer is varied. As apparent from

FIG. 15

, the operating voltage of this semiconductor light-emitting device of the tenth embodiment is 0.07 or more lower than that in the case where the protective layer is not provided (first embodiment, in which the 20 mA operating voltage is 2.1 V). Consequently, the Al composition ratio X of the p-AlGaInP protective layer is, desirably, not more than 0.2 (not more than 20%) as a condition for the operating voltage to be not more than 2.03 V.




(Eleventh Embodiment)




The semiconductor light-emitting device which is an eleventh embodiment of the invention differs from the semiconductor light-emitting device of the first embodiment in that the second cladding layer is a p-Al


0.5


In


0.5


P layer.




In this semiconductor light-emitting device of the eleventh embodiment, the notch occurring at the valence band between the current diffusion layer and the second cladding layer shown in the band junction diagram of

FIG. 2B

is even higher (about 0.29 eV) than that of the semiconductor light-emitting device of the first embodiment. As a result, the 20 mA operating voltage at this interface increases to about 3.7 V (against about 3.5 V of the first embodiment).




On the other hand, the notch occurring at the valence band between the intermediate band gap layer and the second cladding layer shown in the band junction of

FIG. 2C

also becomes higher (about 0.16 eV) than that of the semiconductor light-emitting device of the first embodiment. However, the resultant increase of the 20 mA operating voltage is only about 0.05 V.




Consequently, in this semiconductor light-emitting device, although the 20 mA operating voltage became 2.15 V, being 0.05 V higher than that of the semiconductor light-emitting device of the first embodiment, yet this is no problem practically.





FIG. 16

shows the 20 mA operating voltage resulting when the Al composition ratio X of the p-(Al


x


Ga


1−x


)


0.5


In


0.5


P second cladding layer was varied. In this case, the intermediate band gap layer was given by a layer having a mismatch of −3.1% to GaAs. With the Al composition being not less than 0.6, the operating voltage was not more than 2.5 V, which is a permissible level. On the other hand, with the Al composition ratio X being less than 0.6, the emission intensity decreases (which would be attributed to the fact that a hetero-barrier between p-cladding layer and active layer cannot be obtained). Thus, the Al composition is desirably within a range of 0.6≦×≦1.0.




Also,

FIG. 17

shows the 20 mA operating voltage resulting when the layer thickness of the intermediate layer was varied in the semiconductor light-emitting device of the seventh embodiment shown in FIG.


8


. As can be understood from

FIG. 17

, since the operating voltage increases beyond 2.5 V with the intermediate layer thickness beyond 0.5 μm, the thickness of the intermediate layer is desirably not more than 0.5 μm. The reason that the operating voltage increases with increasing thickness of the intermediate layer can be considered that a resistance component of the intermediate layer itself emerges.




Also,

FIG. 18

shows the 20 mA operating voltage resulting when the carrier concentration of the intermediate layer was varied in the semiconductor light-emitting device of the seventh embodiment shown in FIG.


8


. As can be understood from

FIG. 18

, since the operating voltage increases beyond 2.5 V with the carrier concentration of the intermediate layer being under 0.5×10


18


cm


−3


, the carrier concentration of the intermediate layer is desirably not less than 0.5×10


18


cm


−3


. The reason that the operating voltage increases with decreasing carrier concentration of the intermediate layer can be considered that series resistance of the notch part increases.




(Twelfth Embodiment)





FIGS. 19A

,


19


B,


19


C and


19


D show a semiconductor light-emitting device manufacturing method according to the present invention.




First, an n-GaAs buffer layer


181


with a thickness of 0.5 μm (Si doping: 5×10


17


cm


−3


), an n-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P first cladding layer


182


with a thickness of 1.0 μm (Si doping: 5×10


17


cm


−3


), an undoped (Al


0.3


Ga


0.7


)


0.5


In


0.5


P active layer


183


with a thickness of 0.6 μm, a p-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P second cladding layer


184


with a thickness of 0.7 μm (Zn doping: 5×10


17


cm


−3


), a p-(Al


0.4


Ga


0.6


)


0.9


In


0.1


P intermediate band gap layer


185


with a thickness of 0.15 μm, and a p-GaP protective layer


186


with a thickness of 0.1 μm (Zn doping: 1×10


18


cm


−3


) are stacked one by one on an n-GaAs substrate


190


by MOCVD process (FIG.


19


A).




Subsequently, a pattern is formed with an ordinary photomask, and then device center regions of the protective layer


186


and the intermediate band gap layer


185


are removed by etching, by which a protective layer


186


A and an intermediate band gap layer


185


A each having a circular-shaped removal region are formed (FIG.


19


B).




For example, the 0.1 μm thick p-GaP protective layer


186


can be etched by being dipped for about 1 min. in a solution (50° C.) of H


2


SO


4


:H


2


O


2


:H


2


O=3:1:1, and the p-(Al


0.4


Ga


0.6


)


0.9


In


0.1


P intermediate band gap layer


185


can also be etched by being dipped for about 2 min. in the same solution.




Thereafter, a p-GaP current diffusion layer


187


(Zn doping: 2×10


18


cm


−3


) is grown to a thickness of 6 μm also by MOCVD process (FIG.


19


C).




Next, a first electrode


191


is formed overall under the n-GaAs substrate


190


, while a circular-shaped second electrode


192


is formed over the grown-layer side device center region opposite to the removal region (FIG.


19


D). This grown-layer side second electrode


192


may be formed either by forming an electrode overall on the grown layer side and then using an ordinary photomask, or by selectively depositing the electrode with a metal mask.




With the use of this semiconductor light-emitting device manufacturing method, a heterojunction of type II by the p-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P second cladding layer


184


and the p-GaP current diffusion layer


187


is formed, so that a high-resistance interface can be formed.




In this case, the n-type first cladding layer


182


, the active layer


183


and the p-type second cladding layer


184


need only to be AlGaInP layers that provide lattice matching with GaAs. Also, the p-GaP current diffusion layer


187


needs only to be a semiconductor that forms a heterojunction of type II with the p-type second cladding layer


184


.




(Thirteenth Embodiment)





FIGS. 20A

,


20


B,


20


C and


20


D show a semiconductor light-emitting device manufacturing method which is a thirteenth embodiment of the invention.




First, an n-GaAs buffer layer


201


with a thickness of 0.5 μm (Si doping: 5×10


17


cm


−3


), an n-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P first cladding layer


202


with a thickness of 1.0 μm (Si doping: 5×10


17


cm


−3


) an undoped (Al


0.3


Ga


0.7


)


0.5


In


0.5


P active layer


203


with a thickness of 0.6 μm, a p-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P second cladding layer


204


with a thickness of 0.7 μm (Zn doping: 5×10


17


cm


−3


), a p-(Al


0.4


Ga


0.6


)


0.9


In


0.1


P intermediate band gap layer


205


with a thickness of 0.15 μm, and a p-GaP protective layer


206


with a thickness of 0.1 μm (Zn doping: 1×10


18


cm


3


) are stacked one by one on an n-GaAs substrate


210


by MOCVD process (FIG.


20


A).




Subsequently, a pattern is formed with an ordinary photomask, and then device center regions of the protective layer


206


and the intermediate band gap layer


205


are removed by etching, and further a 0.4 μm thick upper portion of the p-AlGaInP second cladding layer


204


corresponding to the above removal regions is removed by etching. Thus, a protective layer


206


A, an intermediate band gap layer


205


A and a second cladding layer


204


A each having a circular-shaped removal region are formed (FIG.


20


B).




For example, the 0.1 μm thick p-GaP protective layer


206


can be etched by being dipped for about 1 min. in a solution (50° C.) of H


2


SO


4


:H


2


O


2


:H


2


O=3:1:1, and the p-(Al


0.4


Ga


0.6


)


0.9


In


0.1


P intermediate band gap layer


205


can also be etched by being dipped for about 2 min. in the same solution. Next, the p-AlGaInP second cladding layer


204


can be etched to nearly a desired position (remaining thickness: 0.3 μm) by being dipped for about 4 min. in a H


3


PO


4


undiluted solution (40° C.).




Thereafter, a p-GaP current diffusion layer


207


(Zn doping: 2×10


18


cm


−3


) is grown to a thickness of 6 μm also by MOCVD process (FIG.


20


C).




Next, a first electrode


211


is formed overall under the n-GaAs substrate


210


, while a circular-shaped second electrode


212


is formed over the grown-layer side device center region (FIG.


20


D). The grown-layer side second electrode


212


may be formed either by forming an electrode overall on the grown layer side and then using an ordinary photomask, or by selectively depositing the electrode with a metal mask.




With the use of this semiconductor light-emitting device manufacturing method, a heterojunction of type II by the p-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P second cladding layer


204


and the p-GaP current diffusion layer


207


is formed, so that a high-resistance interface can be formed.




In this case, the n-type first cladding layer


202


, the active layer


203


and the p-type second cladding layer


204


need only to be AlGaInP layers that provide lattice matching with GaAs.




Also, the current diffusion layer


207


needs only to be a semiconductor that forms a heterojunction of type II with the p-type second cladding layer


204


.




(Fourteenth Embodiment)





FIGS. 21A

,


21


B,


21


C and


21


D show a semiconductor light-emitting device manufacturing method which is a thirteenth embodiment of the invention.




First, an n-GaAs buffer layer


221


with a thickness of 0.5 μm (Si doping: 5×10


17


cm


−3


), an n-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P first cladding layer


222


with a thickness of 0.6 of 1.0 μm (Si doping: 5×10


17


cm


−3


), an undoped (Al


0.3


Ga


0.7


)


0.5


In


0.5


P active layer


223


with a thickness of 0.6 μm, and a p-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P second cladding layer


224


with a thickness of 0.3 μm (Zn doping: 5×10


17


cm


−3


) are stacked on an n-GaAs substrate


230


by MOCVD process. Then, a p-Ga


05


In


0.5


P etching stop layer


225


with a thickness of 0.01 μm (Zn doping: 5×10


17


cm


−3


), a p-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P third cladding layer


226


with a thickness of 0.4 μm (Zn doping: 5×10


17


cm


−3


), a p-(Al


0.4


Ga


0.6


)


0.9


In


0.1


P intermediate band gap layer


227


with a thickness of 0.15 μm, and a p-GaP protective layer


228


with a thickness of 0.1 μm (Zn doping: 1×10


18


cm


−3


) are stacked one by one (FIG.


21


A).




Subsequently, a pattern is formed with an ordinary photomask, and then device center regions of the protective layer


228


, the intermediate band gap layer


227


and the p-AlGaInP third cladding layer


226


are removed by etching, by which a protective layer


228


A, an intermediate band gap layer


227


A and a third cladding layer


226


A each having a circular-shaped removal region are formed (FIG.


21


B).




For example, the 0.1 μm thick p-GaP protective layer


228


can be etched by being dipped for about 1 min. in a solution (50° C.) of H


2


SO


4


:H


2


O


2


:H


2


O=3:1:1, and the p-(Al


0.4


Ga


0.6


)


0.9


In


0.1


P intermediate band gap layer


227


can also be etched by being dipped for about 2 min. in the same solution. Next, the 0.4 μp thick p-AlGaInP third cladding layer


226


can be completely etched by being dipped for about 5 min. in a H


3


PO


4


undiluted solution (40° C.) . As to the reason of this, although the 0.4 μm thick p-AlGaInP third cladding layer


226


can be generally etched in four min. as described in the semiconductor light-emitting device manufacturing method of the thirteenth embodiment, yet the p-GaInP layer contributes as the etching stop layer


225


and therefore the p-AlGaInP third cladding layer


226


is dipped somewhat longer so that etching irregularities can be eliminated.




Thereafter, a p-GaP current diffusion layer


229


(Zn doping: 2×10


18


cm


−3


) is grown to a thickness of 6 μm also by MOCVD process (FIG.


21


C).




Next, a first electrode


231


is formed overall under the n-GaAs substrate


230


, while a circular-shaped second electrode


232


is formed over the grown-layer side device center region (FIG.


21


D). The grown-layer side second electrode


232


may be formed either by forming an electrode overall on the grown layer side and then using an ordinary photomask, or by selectively depositing the electrode with a metal mask.




With the use of this semiconductor light-emitting device manufacturing method, a heterojunction of type II by the p-Ga


0.5


In


0.5


P etching stop layer


225


and the p-GaP current diffusion layer


229


is formed, so that a high-resistance interface can be formed.




In this case, the n-type first cladding layer


222


, the active layer


223


, the p-type second cladding layer


224


and the third cladding layer


226


need only to be AlGaInP layers that provide lattice matching with GaAs. Also, the current diffusion layer


229


needs only to be a semiconductor that forms a heterojunction of type II with the second cladding layer


224


.




(Fifteenth Embodiment)





FIGS. 22A

,


22


B,


22


C and


22


D show a semiconductor light-emitting device manufacturing method which is a fifteenth embodiment of the invention.




First, by MOCVD process, on an n-GaAs substrate


250


is grown an n-GaAs buffer layer


241


(Si doping: 5×10


17


cm


−3


) to a thickness of 0.5 μm, and then, ten pairs of n-Al


0.5


In


0.5


P layer and n-(Al


0.4


Ga


0.6


)


0.5


In


0.5


P layer are further formed, by which a DBR (optical reflection) layer


242


is formed (thickness of each layer: 0.05 μm, Si doping of each layer: 5×10


17


cm


−3


) . Subsequently, an n-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P first cladding layer


243


with a thickness of 1.0 μm (Si doping: 5×10


17


cm


−3


), an undoped (Al


0.3


Ga


0.7


)


0.5


In


0.5


P active layer


244


with a thickness of 0.6 μm, a p-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P second cladding layer


245


with a thickness of 0.7 μm (Zn doping: 5×10


17


cm


−3


), a p-(Al


0.4


Ga


0.6


)


0.9


In


0.1


P intermediate band gap layer


246


with a thickness of 0.15 μm, and a p-GaP protective layer


247


with a thickness of 0.1 μm (Zn doping: 1×10


18


cm


−3


) are stacked one by one (

FIG. 22A

)




Subsequently, a pattern is formed with an ordinary photomask, and then regions of the protective layer


247


and the intermediate band gap layer


246


other than their device center regions are removed by etching, by which circular-shaped protective layer


247


A and intermediate band gap layer


246


A are formed (FIG.


22


B).




For example, the 0.1 μm thick p-GaP protective layer


247


can be etched by being dipped for about 1 min. in a solution (50° C.) of H


2


SO


4


: H


2


O


2


:H


2


O=3:1:1, and the p-(Al


0.4


Ga


0.6


)


0.9


In


0.1


P intermediate band gap layer


246


can also be etched by being dipped for about 2 min. in the same solution.




Thereafter, a p-(Al


0.05


Ga


0.95


)


0.9


In


0.1


P current diffusion layer


248


(Zn doping: 2×10


18


cm


−3


) is grown to a thickness of 6 μm also by MOCVD process (FIG.


22


C).




Next, a first electrode


251


is formed overall under the n-GaAs substrate


250


, while a second electrode


252


is formed over the region other than the device center region on the grown layer side (FIG.


22


D). The grown-layer side second electrode


252


may be formed either by forming an electrode overall on the grown layer side and then using an ordinary photomask, or by selectively depositing the electrode with a metal mask.




With the use of this semiconductor light-emitting device manufacturing method, a heterojunction of type II by the p-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P second cladding layer


245


and the p(Al


0.05


Ga


0.95


)


0.9


In


0.1


P current diffusion layer


248


is formed, so that a high-resistance interface can be formed.




In this case, the n-type first cladding layer


243


, the active layer


244


and the p-type second cladding layer


245


need only to be AlGaInP layers that provide lattice matching with GaAs. Also, the current diffusion layer


248


needs only to be a semiconductor that forms a heterojunction of type II with the p-type second cladding layer


245


.




(Sixteenth Embodiment)





FIGS. 23A

,


23


B,


23


C and


23


D show a semiconductor light-emitting device manufacturing method which is a sixteenth embodiment of the invention.




First, by MOCVD process, on an n-GaAs substrate


270


is grown an n-GaAs buffer layer


261


(Si doping: 5×10


17


cm


−3


) to a thickness of 0.5 μm, and then, ten pairs of n-Al


0.5


In


0.5


P layer and n-(Al


0.4


Ga


0.6


)


0.5


In


0.5


P layer are further formed, by which a DBR layer


262


is formed (thickness of each layer: 0.05 μm, Si doping of each layer: 5×10


17


cm


−3


). Subsequently, an n-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P first cladding layer


263


with a thickness of 1.0 μm (Si doping: 5×10


17


cm


−3


), an undoped (Al


0.3


Ga


0.7


)


0.5


In


0.5


P active layer


264


with a thickness of 0.6 μm, a p-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P second cladding layer


265


with a thickness of 0.7 μm (Zn doping: 5×10


17


cm


−3


), a p-(Al


0.4


Ga


0.6


)


0.9


In


0.1


P intermediate band gap layer


266


with a thickness of 0.15 μm, and a p-GaP protective layer


267


with a thickness of 0.1 μm (Zn doping: 1×10


18


cm


−3


) are stacked one by one (FIG.


23


A).




Subsequently, a pattern is formed with an ordinary photomask, and then regions of the protective layer


267


and the intermediate band gap layer


266


other than their device center regions are removed by etching, and a 0.3 μm thick upper portion of the p-AlGaInP second cladding layer


265


corresponding to the above removal regions is removed by etching (FIG.


23


B).




For example, the 0.1 μm thick p-GaP protective layer


267


can be etched by being dipped for about 1 min. in a solution (50° C.) of H


2


SO


4


:H


2


O


2


:H


2


O=3:1:1, and the p-(Al


0.4


Ga


0.6


)


0.9


In


0.1


P intermediate band gap layer


266


can also be etched by being dipped for about 2 min. in the same solution. Next, the p-AlGaInP second cladding layer


265


can be etched generally to a desired position (remaining thickness: 0.3 μm) by being dipped for about 4 min. in a H


3


PO


4


undiluted solution (40° C.).




Thereafter, a p-(Al


0.05


Ga


0.95


)


0.9


In


0.1


P current diffusion layer


268


(Zn doping: 2×10


18


cm


−3


) is grown to a thickness of 6μm also by MOCVD process (FIG.


23


C).




Next, a first electrode


271


is formed overall under the n-GaAs substrate


270


, while a second electrode


272


is formed over the region other than the device center region on the grown layer side (FIG.


23


D). The grown-layer side second electrode


272


may be formed either by forming an electrode overall on the grown layer side and then using an ordinary photomask, or by selectively depositing the electrode with a metal mask.




With the use of this semiconductor light-emitting device manufacturing method, a heterojunction of type II by the p-(Al


0.7


Ga


0.3


)


0.5 In




0.5


P second cladding layer


265


and the p-(Al


0.05


Ga


0.95


)


0.9


In


0.1


P current diffusion layer


269


is formed, so that a high-resistance interface can be formed.




In this case, the n-type first cladding layer


263


, the active layer


264


and the p-type second cladding layer


265


need only to be AlGaInP layers that provide lattice matching with GaAs. Also, the current diffusion layer


268


(


269


) needs only to be a semiconductor that forms a heterojunction of type II with the p-type second cladding layer


265


.




(Seventeenth Embodiment)





FIGS. 24A

,


24


B,


24


C and


24


D show a semiconductor light-emitting device manufacturing method which is a seventeenth embodiment of the invention.




First, by MOCVD process, on an n-GaAs substrate


290


is grown an n-GaAs buffer layer


281


(Si doping: 5×10


17


cm


−3


) to a thickness of 0.5 μm, and then, ten pairs of n-Al


0.5


In


0.5


P layer and n-(Al


0.4


Ga


0.6


)


0.5


In


0.5


P layer are further formed, by which a DBR layer


282


is formed (thickness of each layer: 0.05 μm, Si doping of each layer: 5×10


17


cm


−3


). Subsequently, an n-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P first cladding layer


283


with a thickness of 1.0 μm (Si doping: 5×10


17


cm


−3


), an undoped (Al


0.3


Ga


0.7


)


0.5


In


0.5


P active layer


284


with a thickness of 0.6 μm, and a p-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P second cladding layer


285


with a thickness of 0.3 μm (Zn doping: 5×10


17


cm


−3


) are stacked one by one. After this, a p-Ga


0.5


In


0.5


P etching stop layer


286


with a thickness of 0.01 μm (Zn doping: 5×10


17


cm


−3


) a p-(Al


0.7


Ga


0.3


)


0.5


In


0.5


P third cladding layer


287


with a thickness of 0.4 μp (Zn doping: 5×10


17


cm


−3


), a p-(Al


0.4


Ga


0.6


)


0.9


In


0.1


P intermediate band gap layer


288


with a thickness of 0.15 μm, and a p-GaP protective layer


289


with a thickness of 0.1 μm (Zn doping: 1×10


18


cm


−3


) are stacked one by one (FIG.


24


A).




Subsequently, a pattern is formed with an ordinary photomask, and then regions of the protective layer


289


, the intermediate band gap layer


288


and the p-AlGaInP third cladding layer


287


other than their device center regions are removed by etching, by which circular-shaped protective layer


289


A, intermediate band gap layer


288


A and third cladding layer


287


A are formed (FIG.


24


B).




For example, the 0.1 μm thick p-GaP protective layer


289


can be etched by being dipped for about 1 min. in a solution (50° C.) of H


2


SO


4


:H


2


O


2


:H


2


O=3:1:1, and the p-(Al


0.4


Ga


0.6


)


0.9


In


0.1


P intermediate band gap layer


288


can also be etched by being dipped for about 2 min. in the same solution. Next, the 0.4 μp p-AlGaInP third cladding layer


287


can be completely etched by being dipped for about 5 min. in a H


3


PO


4


undiluted solution (40° C.). As to the reason of this, although the 0.4 μp thick p-AlGaInP third cladding layer


287


can be generally etched in four min. as described in the semiconductor light-emitting device manufacturing method of the sixteenth embodiment, yet the p-GaInP layer contributes as the etching stop layer


286


and therefore the p-AlGaInP third cladding layer


287


is dipped somewhat longer so that etching irregularities can be eliminated.




Thereafter, a p-(Al


0.05


Ga


0.95


)


0.9


In


0.1


P current diffusion layer


293


(Zn doping: 2×10


18


cm


−3


) is grown to a thickness of 6 μm also by MOCVD process (FIG.


24


C).




Next, a first electrode


291


is formed overall under the n-GaAs substrate


290


, while a second electrode


272


is formed over the region other than the device center region on the grown layer side (FIG.


24


D). The grown-layer side second electrode


292


may be formed either by forming an electrode overall on the grown layer side and then using an ordinary photomask, or by selectively depositing the electrode with a metal mask.




With the use of this semiconductor light-emitting device manufacturing method, a heterojunction of type II by the p-Ga


0.5


In


0.5


P etching stop layer


286


and the p-(Al


0.05


Ga


0.95


)


0.9


In


0.1


P current diffusion layer


293


is formed, so that a high-resistance interface can be formed.




In this case, the n-type first cladding layer


283


, the active layer


284


and the p-type second cladding layer


285


need only to be AlGaInP layers that provide lattice matching with GaAs. Also, the current diffusion layer


293


needs only to be a semiconductor that forms a heterojunction of type II with the second cladding layer


285


.




Although it has been assumed in the foregoing first to seventeenth embodiments that the first conductive type is n type and the second conductive type is p type, yet it is of course possible that the first conductive type is p type and the second conductive type is n type.




Also, the first electrodes


11


,


31


,


51


,


71


,


91


,


111


,


131


,


151


,


171


,


191


,


211


,


231


,


251


,


271


and


291


have been formed overall on the substrates


10


,


30


,


50


,


70


,


90


,


110


,


130


,


150


,


170


,


190


,


210


,


230


,


250


,


270


and


290


in the foregoing first to seventeenth embodiments. However, those electrodes may be formed partly on the substrates.




Furthermore, although the second electrodes


12


,


32


,


52


,


132


,


152


and


172


as well as the removal regions of the second electrodes


72


,


92


and


112


have been circular-shaped in the first to eleventh embodiments, yet the shape of the second electrodes is not limited to this and may be formed into other shapes such as quadrangular shapes.




The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.



Claims
  • 1. A semiconductor light-emitting device comprising: a first-conductive-type first cladding layer, a first-conductive-type or second-conductive-type or an undoped active layer, a second-conductive-type second cladding layer, a second-conductive-type intermediate band gap layer and a second-conductive-type current diffusion layer, all of which are stacked on one side of a surface of a first-conductive-type semiconductor substrate, a first electrode formed on the other side of the surface of the first-conductive-type semiconductor substrate, and a second electrode formed partly on the second-conductive-type current diffusion layer, whereina region of the second-conductive-type intermediate band gap layer just under the second electrode is removed, and the second-conductive-type current diffusion layer is stacked in the removal region on the second-conductive-type second cladding layer, and wherein a junction plane of the second-conductive-type current diffusion layer and the second-conductive-type second cladding layer has an energy band structure of type II.
  • 2. A semiconductor light-emitting device comprising:a first-conductive-type first cladding layer, a first-conductive-type or second-conductive-type or an undoped active layer, a second-conductive-type second cladding layer, a second-conductive-type intermediate band gap layer and a second-conductive-type current diffusion layer, all of which are stacked on one side of a surface of a first-conductive-type semiconductor substrate, wherein a device center region of the second-conductive-type intermediate band gap layer is removed, and the second-conductive-type current diffusion layer is stacked in the removal region on the second-conductive-type second cladding layer, the second-conductive-type current diffusion layer and the second-conductive-type second cladding layer have an energy band structure in which an upper-end position of valence band and a lower-end position of conduction band are in a type II relation, and wherein the semiconductor light-emitting device further comprises a first electrode formed overall on the other side of the surface of the first-conductive-type semiconductor substrate, and a second electrode formed over the device center region on the second-conductive-type current diffusion layer.
  • 3. The semiconductor light-emitting device according to claim 2, whereinan upper-side portion of a region of the second-conductive-type second cladding layer corresponding to the removal region of the second-conductive-type intermediate band gap layer is removed.
  • 4. A semiconductor light-emitting device comprising:a first-conductive-type first cladding layer, a first-conductive-type or second-conductive-type or an undoped active layer, a second-conductive-type second cladding layer, a second-conductive-type etching stop layer, a second-conductive-type third cladding layer, a second-conductive-type intermediate band gap layer and a second-conductive-type current diffusion layer, all of which are stacked on one side of a surface of a first-conductive-type semiconductor substrate, wherein device center regions of the second-conductive-type intermediate band gap layer and the second-conductive-type third cladding layer are removed, respectively, and the second-conductive-type current diffusion layer is stacked in the removal regions on the second-conductive-type etching stop layer, the second-conductive-type current diffusion layer, the second-conductive-type etching stop layer and the second-conductive-type second cladding layer have an energy band structure in which an upper-end position of valence band and a lower-end position of conduction band are in a type II relation, and wherein the semiconductor light-emitting device further comprises a first electrode formed overall on the other side of the surface of the first-conductive-type semiconductor substrate, and a second electrode formed over the device center region on the second-conductive-type current diffusion layer.
  • 5. The semiconductor light-emitting device according to claim 2, whereinthe removal region at the device center region of the second-conductive-type intermediate band gap layer and the second electrode have generally identical configurations and are opposed to each other.
  • 6. A semiconductor light-emitting device comprising:a first-conductive-type first cladding layer, a first-conductive-type or second-conductive-type or an undoped active layer, a second-conductive-type second cladding layer, a second-conductive-type intermediate band gap layer and a second-conductive-type current diffusion layer, all of which are stacked on one side of a surface of a first-conductive-type semiconductor substrate, wherein a region of the second-conductive-type intermediate band gap layer other than its device center region is removed, and the second-conductive-type current diffusion layer is stacked in the removal region on the second-conductive-type second cladding layer, the second-conductive-type current diffusion layer and the second-conductive-type second cladding layer have an energy band structure in which an upper-end position of valence band and a lower-end position of conduction band are in a type II relation, and wherein the semiconductor light-emitting device further comprises a first electrode formed overall on the other side of the surface of the first-conductive-type semiconductor substrate, and a second electrode formed over the region other than the device center region on the second-conductive-type current diffusion layer.
  • 7. The semiconductor light-emitting device according to claim 6, whereinan upper-side portion of the region of the second-conductive-type second cladding layer opposed to the removal region of the second-conductive-type intermediate band gap layer is removed.
  • 8. A semiconductor light-emitting device comprising: a first-conductive-type first cladding layer, a first-conductive-type or second-conductive-type or an undoped active layer, a second-conductive-type second cladding layer, a second-conductive-type etching stop layer, a second-conductive-type third cladding layer, a second-conductive-type intermediate band gap layer and a second-conductive-type current diffusion layer, all of which are stacked on one side of a surface of a first-conductive-type semiconductor substrate, whereinregions of the second-conductive-type intermediate band gap layer and the second-conductive-type third cladding layer other than their device center regions are removed, respectively, and the second-conductive-type current diffusion layer is stacked in the removal regions on the second-conductive-type etching stop layer, the second-conductive-type current diffusion layer, the second-conductive-type etching stop layer and the second-conductive-type second cladding layer have an energy band structure in which an upper-end position of valence band and a lower-end position of conduction band are in a type II relation, and wherein the semiconductor light-emitting device further comprises a first electrode formed overall on the one side of the surface of the first-conductive-type semiconductor substrate, and a second electrode formed over the region other than the device center region on the second-conductive-type current diffusion layer.
  • 9. The semiconductor light-emitting device according to claim 1, whereina protective layer of the second conductive type is formed on the second-conductive-type intermediate band gap layer.
  • 10. The semiconductor light-emitting device according to claim 1, whereinthe first-conductive-type semiconductor substrate is made of GaAs, the first-conductive-type first cladding layer, the first-conductive-type or second-conductive-type or undoped active layer and the second-conductive-type second cladding layer are made of an AlGaInP-based compound semiconductor that provides lattice matching with GaAs, the second-conductive-type current diffusion layer is made of a GaP- or AlGaInP-based compound semiconductor, and the second-conductive-type intermediate band gap layer is made of an AlGaInP-based compound semiconductor.
  • 11. The semiconductor light-emitting device according to claim 4, whereinthe first-conductive-type semiconductor substrate is made of GaAs, the first-conductive-type first cladding layer, the first-conductive-type or second-conductive-type or undoped active layer, the second-conductive-type second cladding layer, the second-conductive-type etching stop layer 45 and the second-conductive-type third cladding layer are made of an AlGaInP-based compound semiconductor that provides lattice matching with GaAs, the second-conductive-type current diffusion layer is made of a GaP- or AlGaInP-based compound semiconductor, and the second-conductive-type intermediate band gap layer is made of an AlGaInP-based compound semiconductor.
  • 12. The semiconductor light-emitting device according to claim 10, whereinthe second-conductive-type intermediate band gap layer made of the AlGaInP-based compound semiconductor has a rate Δa/a of lattice matching to GaAs falling within a range of −3.2% ≦Δa/a≦−2.5%.
  • 13. The semiconductor light-emitting device according to claim 12, whereinthe second-conductive-type intermediate band gap layer is composed of a plurality of AlGaInP layers having different rates of lattice matching to GaAs, the lattice matching rates Δa/a of those AlGaInP layers each falling within a range of −3.2≦Δa/a≦−2.5%.
  • 14. The semiconductor light-emitting device according to claim 10, whereina second-conductive-type protective layer made of GaP or an AlGaInP-based compound semiconductor having a Al composition ratio of not more than 20% relative to the total of III group is stacked on the second-conductive-type intermediate band gap layer.
  • 15. The semiconductor light-emitting device according to claim 11, whereinthe second-conductive-type second cladding layer and the second-conductive-type third cladding layer both made of an AlGaInP-based compound semiconductor have a composition of (AlxGa1−x)0.5In0.5P (where 0.6 ≦×≦1.0).
  • 16. The semiconductor light-emitting device according to claim 1, whereinthe second-conductive-type intermediate band gap layer has a layer thickness of not more than 0.5 μm.
  • 17. The semiconductor light-emitting device according to claim 1, whereinthe second-conductive-type intermediate band gap layer has a carrier concentration of not less than 0.5×1018 cm−3.
Priority Claims (1)
Number Date Country Kind
2000-120848 Apr 2000 JP
US Referenced Citations (2)
Number Name Date Kind
5777349 Nakamura et al. Jul 1998 A
6298077 He Oct 2001 B1
Foreign Referenced Citations (6)
Number Date Country
40 17 632 Dec 1990 DE
0 702 414 Mar 1996 EP
4-229665 Aug 1992 JP
9-74221 Mar 1997 JP
9-260724 Oct 1997 JP
10-214996 Aug 1998 JP
Non-Patent Literature Citations (1)
Entry
Weisbuch et al, “Quantum Semiconductor Structures, Fundamentals and Applications”, Academic Press, Inc., Harcourt Brace Jovanovich Pubishers, 1991, pp. 3-4.