Nitride semiconductor light emitting device and fabrication method thereof
Provided is a nitride semiconductor light emitting device including: a substrate; a first buffer layer formed above the substrate; an indium-containing second buffer layer formed above the first buffer layer; an indium-containing third buffer layer formed above the second buffer layer; a first nitride semiconductor layer formed above the third buffer layer; an active layer formed above the first nitride semiconductor layer; and a second nitride semiconductor layer formed above the active layer. According to the present invention, the crystal defects are further suppressed, so that the crystallinity of the active layer is enhanced, and the optical power and the operation reliability are enhanced.
1. A method of fabricating a nitride semiconductor light emitting device, the method comprising:
forming a first buffer layer above a substrate;
recrystallizing the first buffer layer at a temperature higher than a growth temperature of the first buffer layer;
forming a second buffer layer containing indium above the first buffer layer;
forming a third buffer layer containing indium and configured to directly contact the second buffer layer;
forming an indium-doped GaN layer above the third buffer layer;
forming a first nitride semiconductor layer configured to directly contact the indium-doped GaN layer;
forming an active layer above the first nitride semiconductor layer; and
forming a second nitride semiconductor layer above the active layer;
wherein the first nitride semiconductor layer is disposed between the indium-doped GaN layer and the active layer, and
wherein the second buffer layer has a growth temperature between the growth temperature of the first buffer layer and the temperature of the recrystallizing of the first buffer layer.
2. The method according to claim 1 , further comprising forming a third nitride semiconductor layer above the second nitride semiconductor layer.
3. The method according to claim 1 , wherein the second buffer layer is grown in a single crystal.
4. The method according to claim 1 , wherein the growth temperature of the first buffer layer is in a range of from 500° C. to 600° C., and wherein the growth temperature of the second buffer layer is in a range of from 750° C. to 850° C.
5. The method according to claim 1 , wherein the indium content contained in the second buffer layer is less than 10%.
6. The method according to claim 1 , wherein the third buffer layer is grown in a single crystal such that the indium content contained therein is decreased.
7. The method according to claim 1 , wherein the third buffer layer has a growth temperature which is higher than that of the second buffer layer and is increased to a growth temperature of the indium-doped GaN layer.
8. The method according to claim 1 , wherein a growth temperature of the indium-doped GaN layer is the same as the temperature of the recrystallizing of the first buffer layer.
9. The method according to claim 1 , wherein the first nitride semiconductor layer is formed by a delta doping in which a concentration of a doped material is periodically varied, and is an n-GaN layer which is delta-doped with silicon/indium or silicon/aluminum.
10. The method according to claim 1 , further comprising forming, between the first nitride semiconductor layer and the active layer, a low-mole indium-doped GaN layer or a low-mole InGaN layer having a bottom surface configured to directly contact the first nitride semiconductor layer, a top surface configured to directly contact the active layer, and an indium content of 1-5%.
11. The method according to claim 1 , wherein the second nitride semiconductor layer is formed by a delta doping in which a concentration of a doped material is periodically varied, and is a p-GaN layer which is delta-doped with magnesium or aluminum or magnesium/aluminum.
12. The method according to claim 2 , wherein the third nitride semiconductor layer is formed in an n-InGaN layer with a super grading structure in which an indium content is varied.
13. The method according to claim 1 , wherein the indium-doped GaN layer is configured to directly contact the third buffer layer.
14. The method according to claim 1 , wherein the third buffer layer has an indium content which is decreased from a bottom surface of the third buffer layer to a top surface of the third buffer layer to grow the third buffer layer having the same single crystal phase as that of the first nitride semiconductor layer.
15. A method of fabricating a nitride semiconductor light emitting device, the method comprising:
forming a first buffer layer above a substrate;
recrystallizing the first buffer layer at a temperature higher than a growth temperature of the first buffer layer;
forming a second buffer layer containing indium above the first buffer layer, wherein the first buffer layer and the second buffer layer each has substantially the same tensile strain as the substrate;
forming a third buffer layer containing indium and configured to directly contact the second buffer layer;
forming an indium-doped GaN layer above the third buffer layer;
forming a first nitride semiconductor layer configured to directly contact the indium-doped GaN layer;
forming an active layer above the first nitride semiconductor layer; and
forming a second nitride semiconductor layer above the active layer,
wherein the second buffer layer has a growth temperature between the growth temperature of the first buffer layer and the temperature of the recrystallizing of the first buffer layer.
16. The method according to claim 15 , further comprising forming a third nitride semiconductor layer above the second nitride semiconductor layer.
17. The method according to claim 15 , wherein the third buffer layer has a growth temperature which is higher than that of the second buffer layer and is increased to a growth temperature of the indium-doped GaN layer.
18. The method according to claim 15 , wherein the growth temperature of the first buffer layer is in a range of from 500° C. to 600° C., and wherein the growth temperature of the second buffer layer is in a range of from 750° C. to 850° C.
19. The method according to claim 15 , wherein a growth temperature of the indium-doped GaN layer is the same as the temperature of the recrystallizing of the first buffer layer.
20. The method according to claim 15 , wherein the third buffer layer has substantially the same indium content as the second buffer layer.