# US 10,121,937 B2 · Light extraction using feature size and shape control in LED surface roughening

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- Number: US 10,121,937 B2
- Document ID: US10121937B2
- Status: Granted
- Kind: B2
- Application number: 15/216,444
- Filed: 2016-07-21
- Published: 2016-11-10
- Granted: 2018-11-06
- Earliest claimed: 2012-06-01
- Assignees: Lumileds LLC
- Applicants: Koninklijke Philips N.V.
- Inventors: Rajwinder Singh; John Edward Epler
- Web page: https://patentgrep.com/patent/US10121937B2

## CPC

- H10H 20/82: Roughened surfaces, e.g. at the interface between epitaxial layers
- H10H 20/01: Manufacture or treatment
- H10H 20/0137: {the light-emitting regions comprising nitride materials}
- H10H 20/018: {Bonding of wafers}
- H10H 20/811: having quantum effect structures or superlattices, e.g. tunnel junctions
- H10H 20/814: having reflecting means, e.g. semiconductor Bragg reflectors
- H10H 20/824: comprising only Group III-V materials, e.g. GaP
- H10H 20/825: containing nitrogen, e.g. GaN
- H10H 20/835: {Reflective materials}
- H10H 20/855: Optical field-shaping means, e.g. lenses
- H10H 20/856: Reflecting means
- H10H 20/036: {of packages}
- H10H 20/0363: {of optical field-shaping means}
- H10H: INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS

## Abstract

The structural characteristics of the light-exiting surface of a light emitting device are controlled so as to increase the light extraction efficiency of that surface when the surface is roughened. A light emitting surface comprising layers of materials with different durability to the roughening process exhibits a higher light extraction efficiency than a substantially uniform light emitting surface exposed to the same roughening process. In a GaN-type light emitting device, a thin layer of AlGaN material on or near the light-exiting surface creates sharper features after etching compared to the features created by conventional etching of a surface comprising only GaN material.

## Claims

### Claim 1

A light emitting device, comprising:
a light emitting structure, comprising:
a light extraction surface, comprising:
an undoped template layer devoid of islanding growth;
a first conductive semiconductor layer on the undoped template layer, the first conductive semiconductor layer being devoid of islanding growth and less durable to etching than the undoped template layer; and
etching features extending into the undoped template layer and the first conductive semiconductor layer, wherein a topology of the etching features at the undoped template layer is sharper than a topology of the etching features at the first conductive semiconductor layer;
an active layer on the first conductive semiconductor layer;
a second conductive semiconductor layer on the active layer, the second conductive semiconductor layer being an opposite polarity as the first conductive semiconductor layer; and
N and P-type contacts on a same surface opposite the light extraction surface.

### Claim 2 (depends on 1)

The device of claim 1, wherein the undoped template layer includes AlGaN and the first conductive semiconductor layer includes GaN.

### Claim 3 (depends on 2)

The device of claim 2, wherein the undoped template layer includes AlxGa1−xN, where x is between 0.3 and 0.8.

### Claim 4 (depends on 1)

The device of claim 1, wherein the undoped template layer and the first conductive semiconductor layers have different material characteristics including at least one of material composition, crystal defect density, type of crystal defects, carrier concentration, and epitaxial stress.

### Claim 5 (depends on 1)

The device of claim 1, wherein the first conductive semiconductor layer comprises a N-type layer and the second conductive semiconductor layer comprises a P-type layer.