This application claims priority to Japanese Patent Application No. 2009-282006 filed on Dec. 11, 2009, the disclosure of which including the specification, the drawings, and the claims is hereby incorporated by reference in its entirety.
The present disclosure relates to semiconductor laser devices and methods of manufacturing the devices; and more particularly to semiconductor laser devices having electrode structures utilizing a junction interface between metal and compound semiconductor, which has a different work function from the metal, and methods of manufacturing the devices.
Source/drain electrodes of a high electron mobility field effect transistor (HEMT) utilizing gallium arsenide (GaAs), which is representative of a compound semiconductor material with a narrow bandgap, exhibit ohmic properties by forming a eutectic alloy of metal and a heavily doped GaAs semiconductor layer. On the other hand, a gate electrode is configured by utilizing a Schottky contact interface between metal and semiconductor. In recent years, power devices utilizing wide-bandgap materials such as gallium nitride (GaN) and silicon carbide (SiC), which have been intensively researched for practical use, all of source/drain electrodes and a gate electrode have electrode structures utilizing Schottky contact interfaces.
A semiconductor light-emitting device utilizing gallium nitride (GaN) will be described below as an example. In an electrode structure of a laser diode (LD), which has rapidly spread as a key device for optical pickup in a high-density optical disk system, and in an electrode structure of a light-emitting diode (LED), which has been put to wide practical use as a illumination light source of an energy saving solid state device in place of conventional illumination sources, contact is obtained by Schottky-connecting metal to a GaN semiconductor layer, as in a gate electrode of a HEMT utilizing GaAs.
A GaN semiconductor laser diode (LD) is a Fabry-Perot laser, in which injected carriers are confined within a quantum well active layer by a p-n double heterostructure. The carriers are injected into the active layer through a contact layer from a Schottky electrode formed on a ridge waveguide structure provided in an upper cladding layer. The ridge waveguide structure limits injected currents, thereby limiting the width of a resonance region for laser oscillation in the active layer. This stabilizes a transverse mode to reduce the operating current. For high-output power operation, a non-current injection region is formed near facets of a ridge waveguide to effectively reduce catastrophic optical damages (CODs) of resonator facets, thereby increasing life expectancy of the device.
As such, in a GaN semiconductor laser diode (LD), establishment of technique of effectively reducing the CODs of resonator facets is required. Also, in order to reduce power consumption and to increase life expectancy, establishment of electrode technique of injecting carriers into an active layer with high efficiency to reduce the operating current by connecting a metal electrode, which is a Schottky electrode formed on a semiconductor surface of a ridge resonator, to the semiconductor surface with stability and low resistance.
As shown in
That is, Japanese Patent Publication No. 2008-034587 shows a conventional technique which reduces CODs due to optical damages in a non-current injection region of the resonator facets and near the resonator facets to increase output power and life expectancy of a semiconductor laser diode. Furthermore, according to the technique shown in Japanese Patent Publication No. 2008-034587, a dielectric film (i.e., the insulating film 106) defining the non-current injection region is formed on the p+-type GaN contact layer (a vertex of the ridge stripe 105) at the side of the resonator facets. Thus, an ohmic p-electrode (i.e., the p-side electrode including the Pd film 103 and the Pt film 104) has facets being in contact with the dielectric film and located on the inner side of the resonator facets. Also, a main p-electrode (i.e., the isolation electrode 107) is formed to cover the dielectric film and the ohmic p-side electrode.
As shown in
That is, in a semiconductor laser element made of a nitride semiconductor material shown in Japanese Patent Publication No. 2008-227002, a facet of the p-electrode 206 is located behind near the resonator surface to avoid problems during a manufacturing process of the element. This prevents removal of an electrode due to impact of cleavage when forming the resonator facet, and improves adhesiveness of the protective films at the side of the resonator facet.
A native oxide layer made of Ga, N, and O and having a thickness of less than about 1 nm exists on a surface of a p+-type GaN layer at a vertex of a ridge resonator, on which a p-electrode (Schottky electrode) made of high work function metal such as Pd, Pt or Ni is formed. Contact characteristics at the connection interface between the p-electrode and the p+-type GaN layer depend on the Fermi level determined by the native oxide layer which is continuous from the semiconductor crystal surface of the region, to which the p-electrode is connected, to the semiconductor crystal surface of the non-current injection region. Thus, the electrode structure needs to be designed in view of not only the p+-type GaN layer of the current injection region at the vertex of the ridge resonator but also the p−-type GaN layer of the non-current injection region, which has a continuous surface with the p+-type GaN layer of the current injection region.
However, in the structure shown in Japanese Patent Publication No. 2008-034587, the main p-electrode covers the ohmic p-electrode, and the dielectric film of the non-current injection region as well. Thus, a change in the Fermi level determined by the interface between the p+-type GaN contact layer and the dielectric film of the non-current injection region, which is continuous with the crystal surface of the p+-type GaN contact layer in the region to which the ohmic p-electrode is connected, affects the Fermi level at the interface between the ohmic p-electrode and the p+-type GaN contact layer, thereby degrading the contact characteristics.
On the other hand, in the structure shown in Japanese Patent Publication No. 2008-227002, the above problem does not occur. However, the dielectric film material used for a facet coating film also coats the non-current injection region when coating the facet. Thus, in accordance with a change in stress characteristics of the dielectric film material, a change in optical characteristics such as a refractive index of the material, or a stoichiometric change of the material; a change in conductivity characteristics on the laser-emitting facet and the like may occur. Therefore, the structure in which the material of the facet coating film is also used as a dielectric film of the non-current injection region is problematic, since the structure impairs the function of the dielectric film of the non-current injection region, which is originally required.
In view of the foregoing, it is an objective of the present disclosure to provide a semiconductor laser device achieving high output power, long life, and a low operation voltage.
The present inventor has found that the following technical means is required to achieve the above-described objective. Specifically, contact resistance between an ohmic p-electrode and a p+-type GaN contact layer need to be reduced by eliminating the influence of a change in the Fermi level at the crystal surface of the p+-type GaN contact layer of a non-current injection region, which is continuous with the crystal surface of the p+-type GaN contact layer of the region to which the ohmic p-electrode is connected (i.e., the connection interface between the dielectric film of the non-current injection region and the p+-type GaN contact layer), on the Fermi level at the interface between the ohmic p-electrode and the p+-type GaN contact layer. In order to eliminate the influence, it is necessary to reduce a change of state of the native oxide layer existing on the surface of the p+-type GaN contact layer which is located near the resonator facet of the semiconductor laser device and is continuous with the surface of the p−-type GaN contact layer of the current injection region (i.e., the surface of the p+-type GaN contact layer in the region in which the dielectric film used for the non-current injection region is in contact with the p+-type GaN contact layer). This reduces problems that the change in the state of the native oxide layer affects the Fermi level at the interface between the ohmic p-electrode and the p+-type GaN contact layer.
The present disclosure was made based on the above findings.
A semiconductor laser device according to the present disclosure includes a substrate; a first conductivity type semiconductor layer, an active layer, a second conductivity type semiconductor layer, and a second conductivity type contact layer, which are sequentially stacked on the substrate; a ridge portion provided in the second conductivity type semiconductor layer and the second conductivity type contact layer, and extending between both facets of a resonator; a current confining layer being in contact with the ridge portion, and having an opening on an upper surface of the ridge portion; a first electrode provided in the opening to be in contact with the second conductivity type contact layer; and a second electrode provided on the first electrode. A non-current injection portion is provided on the upper surface of the ridge portion near the resonator facets to be in contact with the second conductivity type contact layer. The current confining layer and the non-current injection portion are formed of a same dielectric film. The second electrode is spaced apart from an upper surface region of the non-current injection portion.
According to the semiconductor laser device of the present disclosure, the second electrode, which is electrically conductive with (i.e., having the same potential as) the first electrode, is not provided on the dielectric film serving as the non-current injection portion near the resonator facet. Thus, characteristics of the connection interface between the first electrode and the second conductivity type contact layer are not affected by the Fermi level determined by the native oxide layer formed on the crystal surface of the second conductivity type contact layer under the non-current injection portion which is continuous with the crystal surface of the second conductivity type contact layer under the first electrode. Therefore, contact resistance between the first electrode and the second conductivity type contact layer is stable, thereby providing a semiconductor laser device achieving high output power, long life, and low operation voltage.
In the semiconductor laser device according to the present disclosure, the first electrode may be in contact with a sidewall surface of the non-current injection portion.
In the semiconductor laser device according to the present disclosure, the second electrode may extend to a side of the ridge portion to be in contact with the dielectric film in a region other than regions near the resonator facets provided with the non-current injection portion.
In the semiconductor laser device according to the present disclosure, a native oxide layer may be formed on a surface of a part of the second conductivity type contact layer which is in contact with the first electrode. In this case, the native oxide layer may contain elements constituting the second conductivity type contact layer and oxygen. The native oxide layer may have a thickness larger than 0 nm and less than 1 nm.
In the semiconductor laser device according to the present disclosure, a semiconductor multilayer including the first conductivity type semiconductor layer, the active layer, the second conductivity type semiconductor layer, and the second conductivity type contact layer may be made of group III-V nitride compound semiconductor represented by InxAlyGa1-x-yN (where 0≦x≦1, 0≦y≦1, and x+y≦1). With this configuration, the oscillation wavelength of the semiconductor laser device may range from blue violet to green.
In the semiconductor laser device according to the present disclosure, a part of the first electrode being in contact with the upper surface of the second conductivity type contact layer may be made of a single metal or plural metals selected from the group consisting of Pd, Pt, and Ni. With this configuration, a p-electrode, which can be connected with low contact resistance to the p+-type GaN contact layer made of e.g., group III-V nitride compound semiconductor with a wide bandgap, can be formed as a first electrode.
In the semiconductor laser device according to the present disclosure, the dielectric film may be a silicon oxide film. This stabilizes the voltage of the laser to improve the COD level, and improves linearity of current-optical output power (IL) characteristics, thereby mitigating an increase in the operating current according to an increase in the threshold current to enable high-output power operation. Therefore, a semiconductor laser device, which can stably monitor and control optical output power when used in e.g., an optical disk, can be provided.
In the semiconductor laser device according to the present disclosure, a distance between an end of the first electrode and one of the resonator facets may range from 1 μm to 10 μm. This stabilizes the voltage of the laser to improve the COD level, and improves the linearity of IL characteristics, thereby mitigating an increase in the operating current current-optical output power according to an increase in the threshold current to enable high-output power operation. Therefore, a semiconductor laser device, which can stably monitor and control optical output power when used in e.g., an optical disk, can be provided.
A manufacturing method of a semiconductor laser device according to the present disclosure includes the steps of: (a) forming a semiconductor multilayer, in which a first conductivity type semiconductor layer, an active layer, a second conductivity type semiconductor layer, and a second conductivity type contact layer are sequentially stacked on a substrate; (b) forming a ridge portion extending between both facets of a resonator by etching the second conductivity type semiconductor layer and the second conductivity type contact layer; (c) forming a dielectric film on the semiconductor multilayer; (d) after applying first resist onto the dielectric film, deactivating the first resist; (e) exposing a part of the dielectric film located on the ridge portion by etching back the first resist; (f) after applying second resist onto the first resist, performing exposure and development of the second resist, thereby forming an opening in an electrode formation region on the ridge portion; (g) removing a part of the dielectric film located in the electrode formation region by etching using the first resist and the second resist as a mask to expose the upper surface of the ridge portion in the electrode formation region; (h) forming a first electrode film on the exposed portion of the upper surface of the ridge portion, the first resist, and the second resist; and (i) lifting off the first resist and the second resist to remove the first electrode film formed on the first resist and the second resist, thereby forming a first electrode on the upper surface of the ridge portion.
According to the manufacturing method of the semiconductor laser device of the present disclosure, the semiconductor laser device according to the present disclosure, e.g., a GaN semiconductor laser diode (LD), having the above-described features and advantages can be manufactured. Specifically, a change of state of the native oxide layer formed at the connection interface between the upper surface of the ridge portion made of semiconductor and the first electrode is reducible. This controls the Fermi level at the connection interface to stabilize the voltage of the laser, thereby improving the COD level. Therefore, a semiconductor laser device achieving high output power and long life characteristics can be obtained.
Note that, in the manufacturing method of the semiconductor laser device according to the present disclosure, the non-current injection portion defining the non-current injection region, and the current confining layer provided along the extending direction of the ridge portion and having an opening on the upper surface of the ridge portion are formed of a monolithic-integrated dielectric film.
In the manufacturing method of the semiconductor laser device according to the present disclosure, before the step (d), a part of the dielectric film may be etched by dry etching with inert gas. In this case, the inert gas may be argon.
In the manufacturing method of the semiconductor laser device according to the present disclosure, in the step (g), wet etching may be used for etching the dielectric film. In this case, in the step (g), solution containing hydrofluoric acid may be used for etching the dielectric film.
In the manufacturing method of the semiconductor laser device according to the present disclosure, in the step (i), the first resist and the second resist may be lifted off with cleaning agent containing a nitrogen compound. In this case, the cleaning agent containing the nitrogen compound may be cleaning agent containing pyrrolidone.
The manufacturing method of the semiconductor laser device according to the present disclosure may further include after the step (i), the step (j) forming a second electrode on the first electrode. In this case, the second electrode may include a plurality of metal layers, and at least one of the plurality of metal layers may be formed by plating. Furthermore, the at least one metal layer formed by the plating may have a thickness of 1 μm or more. As such, the second electrode, which is smoothly connected to the first electrode even at the step portion, can be formed.
In the manufacturing method of the semiconductor laser device according to the present disclosure, the semiconductor multilayer may be made of group III-V nitride compound semiconductor represented by InxAlyGa1-x-yN (where 0≦x≦1, 0≦y≦1, and x+y≦1). With this configuration, the oscillation wavelength of the semiconductor laser device may range from blue violet to green.
As described above, according to the present disclosure, for example, in a GaN semiconductor laser diode made of a wide-bandgap material, a p-electrode connected to a contact layer with low contact resistance can be provided. Therefore, a semiconductor laser device achieving high output power, long life, and low operation voltage can be provided. Furthermore, by using group nitride compound semiconductor represented by e.g., InxAlyGa1-x-yN (where 0≦x≦1, 0≦y≦1, and x+y≦1), a ridge type laser with an oscillation wavelength ranging from blue violet to green can be realized.
Moreover, according to the present disclosure, the non-current injection portion defining the non-current injection region, and the current confining layer are formed of the monolithic-integrated dielectric film. Therefore, the device can be protected so that physicochemical influence due to the wafer process and the cleavage/coating film formation process does not affect the native oxide layer on the surface of the semiconductor layer which is the upper surface of a ridge waveguide structure.
Furthermore, since the Fermi level at the connection interface between the upper surface of the ridge portion made of semiconductor and the first electrode can be stabilized, low voltage characteristics and the COD level can be improved and an increase in the operating current according to an increase in the threshold current can be mitigated. That is, a ridge type laser enabling low current oscillation and high output power can be realized.
That is, in the present disclosure, by providing a p-electrode operatable at a low voltage, a semiconductor laser device such as a ridge type laser enabling low current oscillation and high output power. Furthermore, the present disclosure is excellent in the COD level, linearity of current-optical output power (IL) characteristics, high-output power operation, and the like, and is particularly useful for applying as a laser light source for optical pickup for example, in a high-density optical disk system.
Embodiment of a semiconductor laser device (semiconductor light-emitting device such as a GaN semiconductor laser diode) according to the present disclosure and a method of manufacturing the device will be described hereinafter in detail with reference to the drawings.
Note that the semiconductor laser device according to the present disclosure is applicable to various types of devices based on the following structure.
Specifically, in the semiconductor laser device according to the present disclosure, a light confining dielectric film of a ridge sidewall serving as a current confining layer, a dielectric film of a non-current injection region, and a p-electrode are formed by self-alignment; and the dielectric films and the p-electrode are symmetric. This reduces deviation of the center of the optical axis. Furthermore, the dielectric film of the non-current injection region and the dielectric film serving as the current confining layer are formed in a monolithic-integrated manner. The p-electrode (Schottky electrode) is formed at a desired position on a ridge portion. The desired position is adjacent to the non-current injection region. This structure reduces physicochemical influence on a contact layer surface during a wafer process, cleavage, or formation of a coating film.
A native oxide layer of semiconductor exists on the contact layer surface on the ridge portion. However, in the manufacturing method of the semiconductor laser device according to the present disclosure, manufacturing processes are performed so that a change of state of the native oxide layer on the contact layer surface of the non-current injection region covered by the dielectric film does not change the electronic state of the contact layer surface of the p-electrode formation region. Specifically, the second electrode provided in a region including the upper surface of the p-electrode and functioning as a pad electrode is spaced apart from the upper surface region of the dielectric film of the non-current injection region. This reduces influence of a change in the Fermi level at the connection interface between the dielectric film of the non-current injection region and e.g., the p+-type GaN contact layer on the Fermi level at the connection interface between the p-electrode and e.g., the p−-type GaN contact layer. Therefore, degradation of the contact characteristics between the p-electrode and the contact layer is reducible.
As shown in
While the wing portion 6b has the structure for mechanically protecting the ridge portion 6a, the wing portion 6b may not be formed.
A p+-type contact layer 7 having e.g., a thickness of about 60 nm and made of p+-type GaN is formed on the upper surfaces of the ridge portion 6a and the wing portion 6b. A native oxide layer containing Ga, N, and O and having a thickness of less than 1 nm exists on the surface of the p+-type contact layer 7. In the following description, the “ridge portion 6a” includes the p+-type contact layer 7.
In a current injection region (see
A dielectric film 8 is formed to cover both side surfaces of the ridge portion 6a of the current injection region, both side surfaces and the upper surface of the ridge portion 6a of the non-current injection region, both side surfaces and the upper surface of the wing portion 6b, and the region between the ridge portion 6a and the wing portion 6b. The dielectric film 8 has an opening for injecting current into the upper surface of the ridge portion 6a. Furthermore, the dielectric film 8 includes a current confining layer 8a formed on both side surfaces of the ridge portion 6a, and a non-current injection portion 8b formed on the upper surface of the ridge portion 6a of the non-current injection region. That is, the current confining layer 8a and the non-current injection portion 8b are formed in a monolithic-integrated manner.
A p-electrode 9 which is a thin film of high work function metal such as Pd, Pt, and Ni, and connected to the p+-type contact layer 7 is formed on the surface of the p+-type contact layer 7 exposed to the opening of the dielectric film 8. The P-electrode 9 covers the upper surface of the p+-type contact layer 7 exposed from the current confining layer 8a, and does not exist on the side surfaces of the ridge portion 6a. Also, the p-electrode 9 does not exist on the dielectric film 8 except for the upper surface of the current confining layer 8a near the side surfaces of the ridge portion 6a. Note that the P-electrode 9 may be in contact with the sidewall surfaces 8c of the non-current injection portion 8b.
A pad electrode 10 is formed on the p-electrode 9. The pad electrode 10 is spaced apart from the non-current injection portion 8b. Note that, in the region other than the region near the resonator facets, in which the p+-type contact layer 7 is in contact with the dielectric film 8 (the non-current injection portion 8b), the pad electrode 10 may extend on a side of the ridge portion 6a to be in contact with the dielectric film 8. As the pad electrode 10, a thin film having a desired multilayer structure capable of reducing metal interdiffusion, for example, a multilayer structure of Ti/Pt/Au and the like. When the pad electrode 10 is formed thick, for example, by using a plated film for a part of the multilayer structure of the pad electrode 10; the lower part of the multilayer structure may be spaced apart from the non-current injection portion 8b, and the upper part of the multilayer structure may be formed by electroplating using a thin film (not shown) connected to the lower part in the wafer surface as an electroplating seed film. This makes the removal process of the electroplating seed film unnecessary, which is required when forming the electroplating seed film over the entire surface of the wafer, thereby simplifying the manufacturing method.
The back surface (the surface opposite to the formation surface of the n-type cladding layer 2 etc.) of the n-type GaN substrate 1 is polished so that the n-type GaN substrate 1 has a desired thickness. An n-electrode 11 connected to the n-type GaN substrate 1 is formed on the back surface. A coating layer 13, which is a thin film having a desired structure, is formed on laser facets (both facets at the front and rear sides) formed by the cleavage process of the wafer.
Some of the features of this embodiment are that the non-current injection region, in which the p+-type contact layer 7 is in contact with the dielectric film 8 (the non-current injection portion 8b) on the upper surface of the ridge portion 6a near the resonator facets, is provided, and that the pad electrode 10 is spaced apart from the upper surface region of the non-current injection portion 8b of the non-current injection region.
According to this embodiment, the pad electrode 10 which is electrically conductive with (i.e., having the same potential as) the p-electrode 9 is not provided on the dielectric film 8 serving as the non-current injection portion 8b near the resonator facets. Thus, characteristics of the connection interface between the p-electrode 9 and the p+-type contact layer 7 are not affected by the Fermi level determined by the native oxide layer formed on the crystal surface of the p+-type contact layer 7 under the non-current injection portion 8b which is continuous with the crystal surface of the p+-type contact layer 7 under the p-electrode 9. Thus, since the contact resistance between the p-electrode 9 and the p+-type contact layer 7 can be reduced, a semiconductor laser device achieving high output power, long life, and a low operation voltage can be provided.
According to this embodiment, the n-type cladding layer 2, the multiple quantum well active layer 4, the p-type cladding layer 6, the p+-type contact layer 7, and the like are made of group III-V nitride compound semiconductor represented by InxAlyGa1-x-y N (where 0≦x≦1, 0≦y≦1, and x+y≦1). Thus, the oscillation wavelength of the semiconductor laser device may range from blue violet to green.
In this embodiment, at least a part of the p-electrode 9, which is in contact with the p+-type contact layer 7, is preferably made of a single metal or plural metals selected from the group consisting of Pd, Pt, and Ni. This enables formation of a p-electrode, which can be connected with low contact resistance to the p+-type GaN contact layer made of e.g., group III-V nitride compound semiconductor with a wide bandgap.
In this embodiment, the dielectric film 8 is preferably a silicon oxide film. This stabilizes the voltage of the laser to improve the COD level, and improves the linearity of current-optical output power (IL) characteristics, thereby mitigating an increase in the operating current according to an increase in the threshold current to enable high-output power operation. Therefore, a semiconductor laser device, which can stably monitor and control optical output power when used in e.g., an optical disk, can be provided.
In this embodiment, the distance between an end of the p-electrode 9 and one of the resonator facets (laser facets) preferably ranges from 1 μm to 10 μm. This stabilizes the voltage of the laser to improve the COD level, and improves the linearity of IL characteristics, thereby mitigating an increase in the operating current according to an increase in the threshold current to enable high-output power operation. Therefore, a semiconductor laser device, which can stably monitor and control optical output power when used in e.g., an optical disk, can be provided.
First, as shown in
Note that the present disclosure is not limited to the above-described semiconductor layers and the manufacturing method, and is clearly applicable even if another growing method of the semiconductor layers and another structures of the semiconductor layers are used.
Next, as shown in
Then, as shown in
After cleaning with the above buffered hydrofluoric acid (BHF), as shown in
In this embodiment, the dielectric film 8 is formed in two steps. The absorption layer 12 contributing to absorption of laser stray light is formed to cover the region from the p+-type contact layer 7 on the wing portion 6b to a point short of reaching the ridge portion 6a by the formation of the dielectric film 8 and spacer liftoff.
Then, as shown in
Next, as shown in
After that, as shown in
Next, as shown in
Next, as shown in
As shown in
Next, as shown in
By the above-described process, the current confining layer 8a located on the side of the ridge portion 6a and made of SiO2 (the dielectric film 8) and the p-electrode 9 are symmetrically formed. Also, the non-current injection portion 8b located on the ridge portion 6a near the resonator facets and made of SiO2 (the dielectric film 8) and the p-electrode 9 are formed in a self-aligned manner. This stabilizes the voltage of the laser to improve the COD level, and improves linearity of current-optical output power (IL) characteristics, thereby mitigating an increase in the operating current according to an increase in the threshold current to enable high-output power operation.
Next, as shown in
As shown in
When the pad electrode 10 is formed thick, for example, by using a plated film for a part of the multilayer structure of the pad electrode 10, the lower part of the multilayer structure may be spaced apart from the non-current injection portion 8b, and the upper part of the multilayer structure may be formed by electroplating, using a thin film connected to the lower part in the wafer surface as an electroplating seed film (not shown). Then, the pad electrode 10 is formed thick (e.g., a thickness of 1 μm or more). This makes the removal process of the electroplating seed film, which is required when forming the electroplating seed film over the entire surface of the wafer, thereby simplifying the manufacturing method.
Next, the back surface (the surface opposite to the formation surface of the n-type cladding layer 2 etc.) of the n-type GaN substrate 1 is polished so that the n-type GaN substrate 1 has a desired thickness. Then, the n electrode 11 connected to the n-type GaN substrate 1 is formed on the back surface. After the cleavage process of the wafer, the coating layer 13 which is a thin film having a desired structure is formed on laser facets (both facets at the front and rear sides) formed by the cleavage. As a result, the structure of the semiconductor laser device according to the embodiments shown in
As shown in
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As shown in
Number | Date | Country | Kind |
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2009-282006 | Dec 2009 | JP | national |