Light emitting diodes (LEDs) with improved light extraction by roughening

• US 7,473,936 B2
• Filed: 12/21/2006
• Issued: 01/06/2009
• Est. Priority Date: 01/11/2005
• Status: Active Grant

• Current Assignee: Foshan Nationstar Semiconductor Co., Ltd. (Foshan Nationstar Optoelectronics Company Limited)
• Original Assignee: SemiLEDs Corporation (SemiLEDs Inc)
• Inventors: Tran, Chuong Anh, Doan, Trung Tri
• Primary Examiner(s): LE, DUNG ANH
• Application Number:
  US11/614,507
• Publication Number:
  US 20070099319A1
• Time in Patent Office: 747 Days
• Field of Search: 257 94- 99, 438 22- 29, 438 48- 52
• US Class Current: 257/95
• CPC Class Codes: H01L 33/0095 Post-treatment of devices, e.g. annealing, recrystallisation or short-circuit elimination
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers

Abstract

Systems and methods are disclosed for fabricating a semiconductor light emitting diode (LED) device by forming an n-gallium nitride (n-GaN) layer on the LED device and roughening the surface of the n-GaN layer to extract light from an interior of the LED device.

Claims

1. A light-emitting diode (LED) device, comprising:

a conductive substrate;

a p-doped layer disposed above the conductive substrate;

an active layer for emitting light disposed above the p-doped layer; and

an n-doped layer disposed above the active layer, wherein a surface of the n-doped layer has been roughened via a photo-electrochemical (PEC) oxidation and etching method, the roughened surface having a non-ordered texture, wherein a dimension of a structure on the roughened surface is approximately one half of the wavelength (λ

/2) of the emitted light for enhanced light extraction from the LED device.

2. The LED device of claim 1, further comprising a conductive contact disposed above the n-doped layer, wherein the contact is used as a mask during the PEC oxidation and etching method.

3. The LED device of claim 1, wherein the root-mean-square (RMS) value of the surface roughness ranges from 0.05 μ

m to 2 μ

m.

4. The LED device of claim 1, wherein the effective refractive index of the roughened surface is approximately 2.0 to 2.5.

5. The LED device of claim 1, further comprising a reflective layer disposed between the conductive substrate and the p-doped layer.

6. The LED device of claim 5, wherein the reflective layer comprises at least one of Ni, Au, Pt, Cr, Ti, Pd, and Ag.