Patent Application
20060043394
1. Field of the Invention
The present invention relates to the gallium-nitride (GaN) based light emitting diode (LED), and in particular to the epitaxy structure of the GaN-based LED.
2. The Prior Arts
Conventionally, a GaN-based LED utilizing indium-gallium-nitride (InGaN) multi-quantum wells (MQWs) technology usually employs a structure whose InGaN MQW active layer is covered and protected by a p-type aluminum-gallium-nitride (AlGaN) cladding layer. Based on the observation from practical operations, however, such a structure has a number of disadvantages. The two severest ones are as follows. First, the lattice constant of the p-type AlGaN cladding layer is very much different from that of the InGaN MQW active layer. Such a significant difference in lattice constants, due to the piezoelectric field effect, would easily cause a stress so strong that the light emitting characteristics of the LED's epitaxy structure is affected. In the worse case, the epitaxy structure itself would be damaged. Secondly, the p-type AlGaN cladding layer would have a better epitaxy structure only when it is grown under a temperature above 1000° C. However, the InGaN MQW active layer is best grown under a temperature between 700° C. and 800° C. Therefore, when the growing temperature is raised above 1000° C. for the p-type AlGaN cladding layer, the InGaN MQW active layer's MQW structure would be damaged, which in turn would affect the lighting efficiency of the GaN-based LED.
To overcome the foregoing disadvantages, the present invention provides a GaN-based LED structure utilizing lattice constant matching technology. The new structure provided by the present invention achieves numerous advantages over the existing GaN-based LED structure according to prior arts.
The principal idea behind the present invention can be best explained with
The purpose of the present invention, therefore, is to use an AlxIn1-xN (0<x<1) material as the p-type cladding layer so that the p-type cladding layer has a lattice constant compatible with that of GaN. The active layer's MQW structure, therefore, would not be damaged from the excessive stress resulted from the incompatible lattice constants during the epitaxial growth of the p-type cladding layer. In addition, another purpose of the present invention can also be seen clearly from
The foregoing and other objects, features, aspects and advantages of the present invention will become better understood from a careful reading of a detailed description provided herein below with appropriate reference to the accompanying drawings.
As shown in
The substrate 11 is made of sapphire (aluminum-oxide monocrystalline). The buffer layer 12 is located upon the substrate 11 and is made of aluminum-gallium-indium-nitride (Al1-a-bGaaInbN, 0≦a, b<1). The n-type GaN contact layer 13 is located upon the buffer layer 12. The active layer 14 is located upon the n-type GaN contact layer 13 and is made of InGaN. The p-type cladding layer 15 on top of the active layer 14 is made of magnesium (Mg)-doped Al1-cIncN (0<c<1) and has a thickness between 50 Å and 3000 Å. The p-type cladding layer 15 is grown under a temperature between 600° C. and 1200° C.
The p-type contact layer 16 on top of the p-type cladding layer 15 is made of Mg-doped GaN.
As shown in
As shown in
The substrate 21 is made of sapphire (aluminum-oxide monocrystalline). The buffer layer 22 is located upon the substrate 21 and is made of Al1-d-eGadIneN (0≦d, e<1). The n-type GaN contact layer 23 is located upon the buffer layer 22. The active layer 24 is located upon the n-type GaN contact layer 23 and is made of InGaN. The p-type cladding layer 25 on top of the active layer 24 is made of Al1-fInfN (0<f<1) doped with Mg and Ga, and has a thickness between 50 Å and 3000 Å. The p-type cladding layer 25 is grown under a temperature between 600° C. and 1200° C.
The p-type contact layer 26 on top of the p-type cladding layer 25 is made of Mg-doped GaN.
As shown in
As shown in
The substrate 31 is made of sapphire (aluminum-oxide monocrystalline). The buffer layer 32 is located upon the substrate 31 and is made of Al1-g-hGagInhN (0≦g, h<1). The n-type GaN contact layer 33 is located upon the buffer layer 32. The active layer 34 is located upon the n-type GaN contact layer 33 and is made of InGaN. The p-type double cladding layer 35 on top of the active layer 34 further contains a first cladding layer 351 and a second cladding layer 352. The first cladding layer 351 on top of the active layer 34 is made of Al1-iIniN (0<i<1) doped with Mg and Ga, and has a thickness between 50 Å and 3000 Å. The first cladding layer 351 is grown under a temperature between 600° C. and 1200° C. The second cladding layer 352 on top of the first cladding layer 351 is made of Mg-doped Al1-jInjN (0<j<1) and has a thickness between 50 Å and 3000 Å. The second cladding layer 352 is grown under a temperature between 600° C. and 1200° C.
The p-type contact layer 36 on top of the p-type double cladding layer 35 is made of Mg-doped GaN.
As shown in
As shown in
The substrate 41 is made of sapphire (aluminum-oxide monocrystalline). The buffer layer 42 is located upon the substrate 41 and is made of Al1-k-lGakInlN (0≦k, l<1). The n-type GaN contact layer 43 is located upon the buffer layer 42. The active layer 44 is located upon the n-type GaN contact layer 43 and is made of InGaN. The p-type double cladding layer 45 on top of the active layer 44 further contains a first cladding layer 451 and a second cladding layer 452. The first cladding layer 451 on top of the active layer 44 is made of Mg-doped Al1-mInmN (0<m<1) and has a thickness between 50 Å and 3000 Å. The first cladding layer 451 is grown under a temperature between 600° C. and 1200° C. The second cladding layer 452 on top of the first cladding layer 451 is made of Al1-nInnN (0<n<1) doped with Mg and Ga, and has a thickness between 50 Å and 3000 Å. The second cladding layer 452 is grown under a temperature between 600° C. and 1200° C.
The p-type contact layer 46 on top of the p-type double cladding layer 45 is made of Mg-doped GaN.
As shown in
Although the present invention has been described with reference to the preferred embodiments, it will be understood that the invention is not limited to the details described thereof. Various substitutions and modifications have been suggested in the foregoing description, and others will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.
