Light extraction using feature size and shape control in LED surface roughening

• US 10,121,937 B2
• Filed: 07/21/2016
• Issued: 11/06/2018
• Est. Priority Date: 06/01/2012
• Status: Active Grant

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Inventors: Singh, Rajwinder, Epler, John Edward
• Primary Examiner(s): Pham, Thanhha
• Application Number:
  US15/216,444
• Publication Number:
  US 20160329466A1
• Time in Patent Office: 838 Days
• CPC Class Codes: H01L 2933/0033 relating to semiconductor body packages
• CPC Class Codes: H01L 2933/0058 relating to optical field-shaping elements
• CPC Class Codes: H01L 33/0025 comprising only AIIIBV compounds
• CPC Class Codes: H01L 33/0075 comprising nitride compounds
• CPC Class Codes: H01L 33/0093 Wafer bonding; Removal of the growth substrate
• CPC Class Codes: H01L 33/0095 Post-treatment of devices, e.g. annealing, recrystallisation or short-circuit elimination
• CPC Class Codes: H01L 33/10 with a light reflecting structure, e.g. semiconductor Bragg reflector
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers
• CPC Class Codes: H01L 33/30 containing only elements of Group III and Group V of the Periodic Table
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01L 33/405 Reflective materials
• CPC Class Codes: H01L 33/58 Optical field-shaping elements
• CPC Class Codes: H01L 33/60 Reflective elements

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

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.

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

3. The device of claim 2, wherein the undoped template layer includes Al_xGa₁₋

xN, where x is between 0.3 and 0.8.

4. 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.

5. 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.