Ultraviolet light-emitting devices incorporating graded layers and compositional offsets

Patent metadata

Field	Value
Publication number	US-10700237-B2
Application number	US-201916239728-A
Country	US
Kind code	B2
Filing date	Jan 4, 2019
Priority date	Sep 17, 2015
Publication date	Jun 30, 2020
Grant date	Jun 30, 2020

Abstract

In various embodiments, light-emitting devices incorporate graded layers with compositional offsets at one or both end points of the graded layer to promote formation of two-dimensional carrier gases and polarization doping, thereby enhancing device performance.

First claim

What is claimed is:

1. A semiconductor device comprising:
a substrate;
an Al v Ga 1-v N layer disposed over the substrate;
a graded Al z Ga 1-z N layer disposed over the Al v Ga 1-v N layer, a composition of the graded Al z Ga 1-z N layer being graded in Al concentration z from a bottom portion to a top portion, such that the Al concentration z monotonically decreases, in a continuous or stepwise fashion, from the bottom portion, in a direction away from the Al v Ga 1-v N layer, to the top portion;
an Al w Ga 1-w N cap layer disposed over the graded Al z Ga 1-z N layer; and
a metallic contact disposed over the Al w Ga 1-w N cap layer and comprising at least one metal,
wherein the Al concentration z of the bottom portion of the graded Al z Ga 1-z N layer is less than an Al concentration v of the Al v Ga 1-v N layer.

2. The device of claim 1 , wherein the substrate has an Al u Ga 1-u N top surface, wherein 0≤u≤1.0.

3. The device of claim 1 , wherein the substrate comprises at least one of silicon carbide, silicon, MgO, Ga 2 O 3 , alumina, ZnO, GaN, InN, or sapphire.

4. The device of claim 1 , wherein 0≤w≤0.4.

5. The device of claim 1 , wherein the Al concentration z of the bottom portion of the graded Al z Ga 1-z N layer is less than an Al concentration v of the Al v Ga 1-v N layer by an amount no less than 0.03.

6. The device of claim 1 , wherein the Al concentration z of the bottom portion of the graded Al z Ga 1-z N layer is less than an Al concentration v of the Al v Ga 1-v N layer by an amount no more than 0.85.

7. The device of claim 1 , wherein the Al concentration z of the bottom portion of the graded Al z Ga 1-z N layer is less than an Al concentration v of the Al v Ga 1-v N layer by an amount no less than 0.03 and by an amount no more than 0.85.

8. The device of claim 1 , wherein the graded Al z Ga 1-z N layer is undoped.

9. The device of claim 1 , wherein a p-type dopant concentration within the graded Al z Ga 1-z N layer is less than 10 13 cm −3 .

10. The device of claim 1 , wherein the graded Al z Ga 1-z N layer is strained.

11. The device of claim 1 , wherein the Al concentration z of the top portion of the graded Al z Ga 1-z N layer is approximately equal to the Al concentration w of the Al w Ga 1-w N cap layer.

12. The device of claim 1 , wherein the Al concentration w of the Al w Ga 1-w N cap layer is approximately 0.

13. The device of claim 1 , wherein a thickness of the Al w Ga 1-w N cap layer is no less than 1 nm and no greater than 50 nm.

14. The device of claim 1 , wherein the Al w Ga 1-w N cap layer is p-type doped.

15. The device of claim 1 , further comprising a Al m Ga 1-m N layer disposed below the Al v Ga 1-v N layer, wherein an Al concentration m of the Al m Ga 1-m N layer is less than the Al concentration z of the bottom portion of the graded Al z Ga 1-z N layer.

16. The device of claim 15 , wherein the Al m Ga 1-m N layer is a portion of a light-emitting device structure.

17. A semiconductor device comprising:
a substrate;
an Al v Ga 1-v N layer disposed over the substrate;
a graded Al z Ga 1-z N layer disposed over the Al v Ga 1-v N layer, a composition of the graded Al z Ga 1-z N layer being graded in Al concentration z from a bottom portion to a top portion, such that the Al concentration z decreases from the bottom portion, in a direction away from the Al v Ga 1-v N layer, to the top portion;
an Al w Ga 1-w N cap layer disposed over the graded Al z Ga 1-z N layer; and
a metallic contact disposed over the Al w Ga 1-w N cap layer and comprising at least one metal,
wherein an Al concentration w of the Al w Ga 1-w N cap layer is less than the Al concentration z of the top portion of the graded Al z Ga 1-z N layer, and
wherein the graded Al z Ga 1-z N layer is undoped or p-type doped with a p-type dopant concentration of less than 10 13 cm −3 .

18. The device of claim 17 , wherein the substrate has an Al u Ga 1-u N top surface, wherein 0≤u≤1.0.

19. The device of claim 17 , wherein the substrate comprises at least one of silicon carbide, silicon, MgO, Ga 2 O 3 , alumina, ZnO, GaN, InN, or sapphire.

20. The device of claim 17 , wherein 0≤w≤0.4.

21. The device of claim 17 , wherein the Al concentration w of the Al w Ga 1-w N cap layer is less than the Al concentration z of the top portion of the graded Al z Ga 1-z N layer by an amount no less than 0.03.

22. The device of claim 17 , wherein the Al concentration w of the Al w Ga 1-w N cap layer is less than the Al concentration z of the top portion of the graded Al z Ga 1-z N layer by an amount no more than 0.85.

23. The device of claim 17 , wherein the Al concentration w of the Al w Ga 1-w N cap layer is less than the Al concentration z of the top portion of the graded Al z Ga 1-z N layer by an amount no less than 0.03 and by an amount no more than 0.85.

24. The device of claim 17 , wherein the graded Al z Ga 1-z N layer is undoped.

25. The device of claim 17 , wherein the p-type dopant concentration within the graded Al z Ga 1-z N layer is less than 10 13 cm −3 .

26. The device of claim 17 , wherein the graded Al z Ga 1-z N layer is strained.

27. The device of claim 17 , wherein the Al concentration z of the bottom portion of the graded Al z Ga 1-z N layer is approximately equal to the Al concentration v of the Al v Ga 1-v N layer.

28. The device of claim 17 , wherein the Al concentration w of the Al w Ga 1-w N cap layer is approximately 0.

29. The device of claim 17 , wherein a thickness of the Al w Ga 1-w N cap layer is no less than 1 nm and no greater than 50 nm.

30. The device of claim 17 , wherein the Al w Ga 1-w N cap layer is p-type doped.

Assignees

• Moe Craig
• Grandusky James R
• Gibb Shawn R
• Schowalter Leo J
• Sato Kosuke
• Morishita Tomohiro
• Crystal Is Inc

Inventors

• Moe Craig
• Grandusky James R
• Gibb Shawn R
• Schowalter Leo J
• Sato Kosuke
• Morishita Tomohiro

Classifications

• H10H20/835

  Reflective materials · CPC title

• H10H20/8215

  characterised by crystalline imperfections, e.g. dislocations; characterised by the distribution of dopants, e.g. delta-doping · CPC title

• H10H20/8162

  Current-blocking structures · CPC title

• H10H20/841

  Reflective coatings, e.g. dielectric Bragg reflectors · CPC title

• H10H20/825

  containing nitrogen, e.g. GaN · CPC title