Pseudomorphic electronic and optoelectronic devices having planar contacts

Patent metadata

Field	Value
Publication number	US-9620676-B2
Application number	US-201615046515-A
Country	US
Kind code	B2
Filing date	Feb 18, 2016
Priority date	Mar 15, 2013
Publication date	Apr 11, 2017
Grant date	Apr 11, 2017

Abstract

In various embodiments, light-emitting devices incorporate smooth contact layers and polarization doping (i.e., underlying layers substantially free of dopant impurities) and exhibit high photon extraction efficiencies.

First claim

What is claimed is:

1. An ultraviolet (UV) light-emitting device comprising:
a substrate having an Al y Ga 1-y N top surface, wherein 1.0≧y≧0.4;
a light-emitting device structure disposed over the substrate, the device structure comprising a plurality of layers each comprising Al x Ga 1-x N;
an undoped graded Al 1-z Ga z N layer disposed over the device structure, a composition of the graded layer being graded in Ga concentration z such that the Ga concentration z increases in a direction away from the light-emitting device structure;
a p-doped Al 1-w Ga w N cap layer disposed over the graded layer, the p-doped Al 1-w Ga w N cap layer having a Ga concentration w, wherein 1.0≧w≧0.8; and
a metallic contact disposed over the Al 1-w Ga w N cap layer and comprising at least one metal.

2. The light-emitting device of claim 1 , wherein the Al 1-w Ga w N cap layer is doped with Mg.

3. The light-emitting device of claim 1 , wherein the Al 1-w Ga w N cap layer is at least partially relaxed.

4. The light-emitting device of claim 1 , wherein the light-emitting device has a photon extraction efficiency of greater than 25%.

5. The light-emitting device of claim 1 , wherein the graded layer and Al 1-w Ga w N cap layer collectively absorb less than 80% of UV photons generated by the light-emitting device structure and having a wavelength less than 340 nm.

6. The light-emitting device of claim 1 , wherein the at least one metal of the metallic contact comprises Ni/Au or Pd.

7. The light-emitting device of claim 1 , wherein the metallic contact has a reflectivity to light generated by the light-emitting device structure of approximately 60% or less.

8. The light-emitting device of claim 1 , wherein the metallic contact has a reflectivity to light generated by the light-emitting device structure of approximately 30% or less.

9. The light-emitting device of claim 1 , wherein the metallic contact has the form of a plurality of discrete lines and/or pixels of the at least one metal, portions of the Al 1-w Ga w N cap layer not being covered by the metallic contact.

10. The light-emitting device of claim 9 , further comprising a reflector disposed over the metallic contact and the uncovered portions of the Al 1-w Ga w N cap layer.

11. The light-emitting device of claim 10 , wherein the reflector comprises a metal having greater than 90% reflectivity to UV light and a work function less than approximately 4.5 eV.

12. The light-emitting device of claim 10 , wherein the reflector has a contact resistivity to the Al 1-w Ga w N cap layer of greater than approximately 5 mΩ-cm 2 .

13. The light-emitting device of claim 10 , wherein the reflector has a contact resistivity to the Al 1-w Ga w N cap layer of greater than approximately 10 mΩ-cm 2 .

14. The light-emitting device of claim 10 , wherein the reflector comprises Al.

15. The light-emitting device of claim 1 , wherein the light-emitting device comprises a light-emitting diode.

16. The light-emitting device of claim 1 , wherein a bottom portion of the graded layer proximate the active device structure has a Ga concentration z substantially equal to a Ga concentration of a layer directly thereunder.

17. The light-emitting device of claim 1 , wherein the substrate consists essentially of doped or undoped AlN.

18. The light-emitting device of claim 1 , wherein the Al 1-w Ga w N cap layer has a thickness between approximately 2 nm and approximately 30 nm.

19. The light-emitting device of claim 1 , wherein the Al 1-w Ga w N cap layer has a surface roughness of less than approximately 6 nm over a sample size of approximately 200 μm×300 μm.

20. The light-emitting device of claim 1 , wherein the metallic contact has a contact resistivity to the Al 1-w Ga w N cap layer of less than approximately 1.0 mΩ-cm 2 .

21. The light-emitting device of claim 1 , wherein a top portion of the graded layer has a Ga concentration z of approximately 1.

22. The light-emitting device of claim 1 , wherein the Ga concentration w of the p-doped Al 1-w Ga w N cap layer is approximately 1.

23. The light-emitting device of claim 1 , wherein the substrate comprises a substrate material and a Al y Ga 1-y N material disposed thereover.

24. The light-emitting device of claim 23 , wherein the substrate material comprises at least one of silicon carbide, silicon, or sapphire.

25. The light-emitting device of claim 23 , wherein the Al y Ga 1-y N material is substantially fully lattice relaxed.

26. The light-emitting device of claim 23 , wherein the Al y Ga 1-y N material has a thickness of at least 1 μm.

27. The light-emitting device of claim 1 , wherein the light-emitting device is a laser.

28. The light-emitting device of claim 1 , wherein a threading dislocation density of at least one of the Al 1-w Ga w N cap layer or the light-emitting device structure is less than 10 5 cm −2 .

29. The light-emitting device of claim 1 , wherein the graded layer has a thickness between approximately 10 nm and approximately 50 nm.

Assignees

• Grandusky James R
• Schowalter Leo J
• Jamil Muhammad
• Mendrick Mark C
• Gibb Shawn R
• Crystal Is Inc

Inventors

• Grandusky James R
• Schowalter Leo J
• Jamil Muhammad
• Mendrick Mark C
• Gibb Shawn R

Classifications

• H01L33/46

  Electricity · mapped topic

• H01L33/387

  Electricity · mapped topic

• H01L33/12 Primary

  Electricity · mapped topic

• H01L33/14

  Electricity · mapped topic

• H01L33/32

  Electricity · mapped topic