Pseudomorphic electronic and optoelectronic devices having planar contacts

Patent metadata

Field	Value
Publication number	US-9299880-B2
Application number	US-201414208379-A
Country	US
Kind code	B2
Filing date	Mar 13, 2014
Priority date	Mar 15, 2013
Publication date	Mar 29, 2016
Grant date	Mar 29, 2016

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 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 (i) a thickness between approximately 2 nm and approximately 30 nm, (ii) a surface roughness of less than approximately 6 nm over a sample size of approximately 200 μm×300 μm, and (iii) a Ga concentration w≧0.8; and
a metallic contact disposed over the Al 1-w Ga w N cap layer and comprising at least one metal, the metallic contact having a contact resistivity to the Al 1-w Ga w N cap layer of less than approximately 1.0 mΩ-cm 2 .

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 (i) 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 and (ii) a top portion of the graded layer opposite the bottom portion of the graded layer has a Ga concentration z of approximately 1.

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

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

• H10H20/8316

  Multi-layer electrodes comprising at least one discontinuous layer · CPC title

• H10H20/833

  Transparent materials · CPC title

• H10H20/811

  having quantum effect structures or superlattices, e.g. tunnel junctions · CPC title

• H10H20/0363

  of optical field-shaping means · CPC title

• H10H20/034

  of coatings · CPC title