# US 8,772,757 B2 · Deep ultraviolet light emitting devices and methods of fabricating deep ultraviolet light emitting devices

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- Number: US 8,772,757 B2
- Document ID: US8772757B2
- Status: Granted
- Kind: B2
- Application number: 12/030,539
- Filed: 2008-02-13
- Published: 2008-06-19
- Granted: 2014-07-08
- Earliest claimed: 2005-05-27
- Assignees: Cree, Inc.
- Applicants: David Todd Emerson; Michael John Bergmann; Amber Abare; Kevin Haberern
- Inventors: David Todd Emerson; Michael John Bergmann; Amber Abare; Kevin Haberern
- Web page: https://patentgrep.com/patent/US8772757B2

## CPC

- H10H 20/815: having stress relaxation structures, e.g. buffer layers
- B82Y 20/00: Nanooptics, e.g. quantum optics or photonic crystals
- H10H 20/825: containing nitrogen, e.g. GaN
- H10H 20/812: within the light-emitting regions, e.g. having quantum confinement structures
- H10H: INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
- B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES

## Abstract

Light emitting devices and methods of fabricating light emitting devices that emit at wavelengths less than 360 nm with wall plug efficiencies of at least than 4% are provided. Wall plug efficiencies may be at least 5% or at least 6%. Light emitting devices and methods of fabricating light emitting devices that emit at wavelengths less than 345 nm with wall plug efficiencies of at least than 2% are also provided. Light emitting devices and methods of fabricating light emitting devices that emit at wavelengths less than 330 nm with wall plug efficiencies of at least than 0.4% are provided. Light emitting devices and methods of fabricating light emitting devices having a peak output wavelength of not greater than 360 nm and an output power of at least 5 mW, having a peak output wavelength of 345 nm or less and an output power of at least 3 mW and/or a peak output wavelength of 330 nm or less and an output power of at least 0.3 mW at a current density of less than about 0.35 μA/μm2 are also provided. The semiconductor light emitting devices may have a direct current lifetime of at least 100 hours, at least 500 hours or at least 1000 hours.

## Claims

### Claim 1

A light emitting device, comprising:
a low defect density base structure comprising:
a substrate;
a GaN-based buffer layer having a first smooth surface that is directly on the substrate and a second smooth surface that is remote from the substrate;
a dielectric layer on the second smooth surface that is remote from the substrate; and
a GaN layer on the dielectric layer remote from the GaN-based buffer layer;
a quantum well active region on the low defect density base structure that emits light, the quantum well active region comprising:
a first barrier layer comprising AlGaN;
a first well layer comprising GaN directly on the first barrier layer;
a second barrier layer comprising AlGaN directly on the first well layer;
a second well layer comprising GaN directly on the second barrier layer; and
a third barrier layer comprising AlGaN directly on the second well layer;
an AlGaN layer on the quantum well active region; and
a GaN based contact layer on the AlGaN layer.

### Claim 2 (depends on 1)

The light emitting device of claim 1 having a wall plug efficiency of at least 4%.

### Claim 3 (depends on 2)

The light emitting device of claim 2, wherein the wall plug efficiency is at least 5%.

### Claim 4 (depends on 2)

The light emitting device of claim 2, wherein the wall plug efficiency is at least 6%.

### Claim 5 (depends on 2)

The light emitting device of claim 2, wherein the light emitting device has a direct current lifetime of at least 100 hours.

### Claim 6 (depends on 2)

The light emitting device of claim 2, wherein the light emitting device has a direct current lifetime of at least 500 hours.

### Claim 7 (depends on 2)

The light emitting device of claim 2, wherein the light emitting device has a direct current lifetime of at least 1000 hours.

### Claim 8 (depends on 2)

The light emitting device of claim 2, wherein the wall plug efficiency is provided at a current density of less than about 0.35 μA/μm2.

### Claim 9 (depends on 1)

The light emitting device of claim 1, wherein the AlGaN layer on the quantum well active region comprises an AlGaN layer doped with a p-type dopant on the quantum well active region and the GaN based contact layer on the AlGaN layer comprises a GaN based contact layer doped with a p-type dopant.

### Claim 10 (depends on 9)

The light emitting device of claim 9, wherein the p-type dopant comprises Mg.

### Claim 11 (depends on 1)

The light emitting device of claim 1, wherein the first and second barrier layers are doped with Si.

### Claim 12 (depends on 1)

The light emitting device of claim 1, wherein the quantum well active region comprises ten quantum well layers and eleven barrier layers with the quantum well layers being disposed between adjacent barrier layers.

### Claim 13 (depends on 1)

The light emitting device of claim 1, wherein the light emitting device including the low defect density base structure, the quantum well active region, the AlGaN layer and the GaN based contact layer has an overall thickness of less than about 2.5 μm.

### Claim 14 (depends on 1)

The light emitting device of claim 1 wherein the substrate comprises SiC.

### Claim 15 (depends on 1)

The light emitting device of claim 1 wherein the dielectric layer comprises a discontinuous dielectric layer.

### Claim 16 (depends on 1)

The light emitting device of claim 1
wherein the dielectric layer comprises a plurality of mask regions.

### Claim 17 (depends on 16)

The light emitting device of claim 16 wherein the mask regions comprise SiN.

### Claim 18 (depends on 1)

The light emitting device of claim 1 wherein the GaN layer on the dielectric layer is less than about 2 μm thick.

### Claim 19 (depends on 1)

The light emitting device of claim 1 wherein the well layer comprises AlGaN and wherein the first and second barrier layers comprise AlGaN having a different concentration of Al than the well layer.

### Claim 20 (depends on 1)

The light emitting device of claim 1 wherein the quantum well active region is configured to emit ultraviolet light.

### Claim 21 (depends on 1)

The light emitting device of claim 1 wherein the quantum well active region is configured to emit light at a peak output wavelength of not greater than 360 nm.

### Claim 22 (depends on 1)

The light emitting device of claim 1 wherein the quantum well active region is configured to emit light at a peak output wavelength of not greater than 345 nm.

### Claim 23 (depends on 1)

The light emitting device of claim 1 wherein the quantum well active region is configured to emit light at a peak output wavelength of not greater than 330 nm.

### Claim 24 (depends on 1)

The light emitting device of claim 1 wherein the GaN layer on the dielectric layer is doped with n-type dopants.

### Claim 25 (depends on 24)

The light emitting device of claim 24, wherein the GaN layer doped with n-type dopants comprises a doped GaN layer having a defect density of less than about 4×108 cm−2.

### Claim 26 (depends on 24)

The light emitting device of claim 24, wherein the GaN layer doped with n-type dopants comprises GaN doped with silicon.

### Claim 27 (depends on 24)

The light emitting device of claim 24 wherein the GaN layer on the dielectric layer is less than about 2 μm thick.

### Claim 28

A method of fabricating a light emitting device, comprising:
forming a low defect density base structure comprising:
a substrate;
a GaN-based buffer layer having a first smooth surface that is directly on the substrate and a second smooth surface that is remote from the substrate;
a dielectric layer on the second smooth surface that is remote from the substrate; and
a GaN layer on the dielectric layer remote from the GaN-based buffer layer;
forming a quantum well active region on the low defect density base structure that emits light, the quantum well active region comprising:
a first barrier layer comprising AlGaN;
a first well layer comprising GaN directly on the first barrier layer;
a second barrier layer comprising AlGaN directly on the first well layer;
a second well layer comprising GaN directly on the second barrier layer; and
a third barrier layer comprising AlGaN directly on the second well layer;
forming an AlGaN layer on the quantum well active region; and
forming a GaN based contact layer on the AlGaN layer.

### Claim 29 (depends on 28)

The method of claim 28 wherein the light emitting device has a wall plug efficiency of at least 4%.

### Claim 30 (depends on 28)

The method of claim 28 wherein the light emitting device has a direct current lifetime of at least 100 hours.

### Claim 31 (depends on 28)

The method of claim 28 wherein the light emitting device has an output power of at least 3 mW at a current density of about 0.35 μA/μm2.

### Claim 32 (depends on 28)

The method of claim 28 wherein the dielectric layer comprises a discontinuous dielectric layer.

### Claim 33 (depends on 28)

The method of claim 28 wherein the dielectric layer comprises a plurality of mask regions.

### Claim 34 (depends on 33)

The method of claim 33 wherein the mask regions comprise SiN.

### Claim 35 (depends on 28)

The method of claim 28 wherein the GaN layer on the dielectric layer is less than about 2 μm thick.

### Claim 36 (depends on 28)

The method of claim 28 wherein the well layer comprises AlGaN and wherein the first and second barrier layers comprise AlGaN having a different concentration of Al than the well layer.

### Claim 37 (depends on 28)

The method of claim 28 wherein the quantum well active region is configured to emit ultraviolet light.

### Claim 38 (depends on 28)

The method of claim 28 wherein the quantum well active region is configured to emit light at a peak output wavelength of not greater than 360 nm.

### Claim 39 (depends on 28)

The method of claim 28 wherein the quantum well active region is configured to emit light at a peak output wavelength of not greater than 345 nm.

### Claim 40 (depends on 28)

The method of claim 28 wherein the quantum well active region is configured to emit light at a peak output wavelength of not greater than 330 nm.

### Claim 41 (depends on 28)

The method of claim 28 wherein the GaN layer on the dielectric layer is doped with n-type dopants.

### Claim 42 (depends on 41)

The method of claim 41 wherein the GaN layer on the dielectric layer is less than about 2 μm thick.