III-nitride light emitting device with reduced polarization fields
View Patent ↗A semiconductor light emitting device includes a light emitting layer sandwiched between two spacer layers. The difference between the net polarization in at least one of the spacer layers and the net polarization in the light emitting layer is less than in the device with conventional spacer layers, such as GaN spacer layers. The difference between the net polarization in at least one of the spacer layers and the net polarization in the light emitting layer is less than about 0.02 C/m 2 . In some embodiments, at least one of the spacer layers is a quaternary alloy of aluminum, indium, gallium, and nitrogen.
1. A semiconductor light emitting device comprising:
first and second spacer layers; and
a light emitting layer sandwiched between the first and second spacer layers;
wherein a difference between a net polarization in at least one of the spacer layers and a net polarization in the light emitting layer is less than a difference between a net polarization in GaN and the net polarization in the light emitting layer, and a difference between the net polarization in at least one of the spacer layers and the net polarization in the light emitting layer is less than 0.02 C/m 2 .
2. The device of claim 1 wherein at least one of the spacer layers comprises Al x In y Ga z N, where 0<x≦1, 0<y≦1, and 0<z≦1.
3. The device of claim 1 wherein the light emitting layer comprises at least one layer of InGaN.
4. The device of claim 1 wherein the difference between the net polarization in at least one of the spacer layers and the net polarization in the light emitting layer is less than 0.01 C/m 2 .
5. The device of claim 1 wherein the difference between the net polarization in at least one of the spacer layers and the net polarization in the light emitting layer is less than 0.005 C/m 2 .
6. The device of claim 1 wherein the difference between the net polarization in at least one of the spacer layers and the net polarization in the light emitting layer is about 0 C/m 2 .
7. The device of claim 1 wherein a difference between a band gap in at least one of the spacer layers and a band gap in the light emitting layer is greater than 0.1 eV.
8. The device of claim 1 wherein a difference between a band gap in at least one of the spacer layers and a band gap in the light emitting layer is greater than 0.2 eV.
9. The device of claim 1 wherein the light emitting layer comprises at least one InGaN layer with a composition between In 0.05 Ga 0.95 N and In 0.5 Ga 0.85 N.
10. The device of claim 9 wherein at least one of the spacer layers is a quaternary alloy of aluminum, indium, gallium, and nitrogen.
11. The device of claim 9 wherein at least one of the spacer layers is a quaternary alloy of aluminum, indium, gallium, and nitrogen; and
an aluminum composition in the quaternary alloy spacer layer is greater than zero and less than or equal to 20%; and
an indium composition in the quaternary alloy spacer layer is greater than zero and less than or equal to 22%.
12. The device of claim 9 wherein:
at least one of the spacer layers is a quaternary alloy of aluminum, indium, gallium, and nitrogen; and
an aluminum composition in the quaternary alloy spacer layer is greater than or equal to 20%.
13. The device of claim 12 wherein the indium composition in the quaternary alloy spacer layer is greater than or equal to 22%.
14. The device of claim 1 wherein the light emitting layer comprises at least one InGaN layer with a composition between In 0.15 Ga 0.85 N and In 0.5 Ga 0.5 N.
15. The device of claim 14 wherein at least one of the spacer layers is a quaternary alloy of aluminum, indium, gallium, and nitrogen.
16. The device of claim 14 wherein at least one of the spacer layers is a quaternary alloy of aluminum, indium, gallium, and nitrogen; and
an aluminum composition in the quaternary alloy spacer layer is greater than zero and less than or equal to 17%; and
an indium composition in the quaternary alloy spacer layer is greater than zero and less than or equal to 28%.
17. The device of claim 14 wherein:
at least one of the spacer layers is a quaternary alloy of aluminum, indium, gallium, and nitrogen; and
an aluminum composition in the quaternary alloy spacer layer is greater than or equal to 17%.
18. The device of claim 17 wherein the indium composition in the quaternary alloy spacer layer is greater than or equal to 28%.
19. The device of claim 1 wherein at least one of the spacer layers has a thickness between about 200 angstroms and about 1000 angstroms.
20. The device of claim 1 wherein at least one of the spacer layers has a thickness between about 200 angstroms and a critical thickness of the spacer layer.
21. The device of claim 1 further comprising:
an n-type region adjacent to a surface of the first spacer layer opposite the light emitting layer; and
a p-type region adjacent to a surface of the second spacer layer opposite the light emitting layer.
22. The device of claim 21 further comprising a highly doped region of n-type material adjacent to an interface between the first spacer layer and the n-type region, the highly doped region of n-type material having a dopant concentration between about 1×10 18 cm −3 and about 1×10 20 cm −3 and a thickness between about 10 angstroms and about 100 angstroms.
23. The device of claim 22 wherein the highly doped region of n-type material has a dopant concentration between about 5×10 19 cm −3 and about 1×10 20 cm −3 .
24. The device of claim 22 wherein the highly doped region of n-type material is located within the first spacer layer.
25. The device of claim 22 wherein the highly doped region of n-type material is located within the n-type region.
26. The device of claim 21 further comprising a highly doped region of p-type material adjacent to an interface between the second spacer layer and the p-type region, the highly doped region of p-type material having a dopant concentration between about 1×10 18 cm −3 and about 1×10 20 cm −3 and a thickness between about 10 angstroms and about 100 angstroms.
27. The device of claim 26 wherein the highly doped region of p-type material has a dopant concentration between about 5×10 19 cm −3 and about 1×10 20 cm −3 .
28. The device of claim 26 wherein the highly doped region of p-type material is located within the second spacer layer.
29. The device of claim 26 wherein the highly doped region of p-type material is located within the p-type region.
30. The device of claim 1 wherein the light emitting layer is a first quantum well, the device further comprising a second quantum well, and a barrier layer disposed between the first quantum well and the second quantum well.
31. The device of claim 30 wherein the barrier layer comprises Al x In y Ga z N, where 0<x≦1, 0<y≦1, and 0<z≦1.
32. The device of claim 30 wherein a net polarization in the barrier layer is less than a net polarization in GaN, and a difference between the net polarization in the barrier layer and a net polarization in at least one of the quantum wells is less than 0.02 C/m 2 .
33. The device of claim 30 wherein the difference between the net polarization in the barrier layer and the net polarization in at least one of the quantum wells is less than 0.01 C/m 2 .
34. The device of claim 30 wherein the difference between the net polarization in the barrier layer and the net polarization in at least one of the quantum wells is less than 0.005 C/m 2 .
35. The device of claim 30 wherein the difference between the net polarization in the barrier layer and the net polarization in at least one of the quantum wells is about 0 C/m 2 .
36. The device of claim 1 wherein the light emitting layer comprises Al x In y Ga z N, where 0<x≦1, 0<y≦1, and 0<z≦1.
37. A semiconductor light emitting device comprising:
first and second spacer layers; and
an active region sandwiched between the first and second spacer layers, the active region comprising a first quantum well, a second quantum well, and a barrier layer disposed between the first quantum well and the second quantum well;
wherein a difference between a net polarization in the barrier layer and a net polarization in at least one of the quantum wells is less than a difference between a net polarization in GaN and the net polarization in at least one of the quantum wells, and a difference between the net polarization in the barrier layer and the net polarization in at least one of the quantum wells is less than 0.02 C/m 2 .
38. The device of claim 37 wherein the barrier layer comprises Al x In y Ga z N, where 0<x≦1, 0<y≦1, and 0<z≦1.
39. The device of claim 37 wherein the difference between the net polarization in the barrier layer and the net polarization in at least one of the quantum wells is less than 0.01 C/m 2 .
40. The device of claim 37 wherein the difference between the net polarization in the barrier layer and the net polarization in at least one of the quantum wells is less than 0.005 C/m 2 .
41. The device of claim 37 wherein the difference between the net polarization in the barrier layer and the net polarization in at least one of the quantum wells is about 0 C/m 2 .