Interface texturing for light-emitting device

• US 6,661,028 B2
• Filed: 05/14/2002
• Issued: 12/09/2003
• Est. Priority Date: 08/01/2000
• Status: Active Grant

• Current Assignee: Epistar Corporation
• Original Assignee: United Epitaxy Company (Epistar Corporation)
• Inventors: Chang, Chih-Sung, Chen, Tzer-Perng, Chang, Holin
• Primary Examiner(s): Nhu, David
• Application Number:
  US10/143,985
• Publication Number:
  US 20020134985A1
• Time in Patent Office: 574 Days
• Field of Search: 257/76, 257/78, 257/79, 257/82, 257/88, 257/200, 257/201, 257/544, 257/614, 257/615, 257/911, 257/918
• US Class Current: 257/79
• CPC Class Codes: H01L 33/02 characterised by the semiconductor bodies
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers
• CPC Class Codes: Y10S 257/918 Light emitting regenerative switching device, e.g. light emitting scr arrays, circuitry

Abstract

The present invention discloses a light-emitting device (LED) with a textured interface formed by utilizing holographic lithography. Two coherent light beams are overlaid to cause constructive and destructive interference and thereby periodical alternative bright and dark lines are formed. A wafer coated with a photoresist material is exposed under the interference lines. After a developing step, a photoresist pattern with textured surface is formed on the wafer. Thereafter, the textured photoresist pattern is transferred to the wafer by etching process and result in a desired light-emitting device with a textured interface.

Claims

1. A semiconductor epitaxial structure for a light-emitting device, comprising:

a first window layer;

a p-n junction active layer stacked on the first window layer; and

a second window layer stacked on the p-n junction active layer, and the second window layer having a textured surface, wherein the textured surface is caused by a plurality of interference lines formed by a plurality of overlaid coherent light beams, and a method of forming the textured surface comprises;

forming a photoresist layer on the second window layer;

performing a first exposure process, which is to project the interference lines formed by the overlaid coherent light beams to the photoresist layer;

rotating the photoresist layer 60 degrees;

performing a second exposure process, which is to project the interference lines formed by the overlaid coherent light beams to the photoresist layer;

rotating the photoresist layer 60 degrees in the same direction continuously;

performing a third exposure process, which is to project the interference lines formed by the overlaid coherent light beams to the photoresist layer;

performing a developing process to form a textured pattern on a surface of the photoresist layer; and

performing an etching process to transfer the textured pattern of the photoresist layer to the second window layer.

2. The structure according to claim 1, wherein a material of the p-n junction active layer is selected from a group consisting of GaAs and Al_xGa₁₋

xAs, and a material of the first window layer and the second window layer is selected from a group consisting of GaAs and Al_yGa<sub>1−

y</sub>As (0≦

x<

y), and an energy gap of the p-n junction active layer is smaller than an energy gap of the first window layer and the second window layer.

3. The structure according to claim 1, wherein a material of the p-n junction active layer is selected from a group consisting of GaInP and (Al_xGa₁₋

x)_zInP, and a material of the first window layer and the second window layer is selected from a group consisting of GaInP and (Al_yGa<sub>1−

y</sub>)_xInP (0≦

x<

y), and an energy gap of the p-n junction active layer is smaller than an energy gap of the first window layer and the second window layer.

4. The structure according to claim 1, wherein after performing the first exposure process, further comprises:

rotating the photoresist layer 90 degrees; and

performing an additional exposure process, which is to project the interference lines formed by the overlaid coherent light beams to the photoresist layer.

5. The structure according to claim 1, wherein the overlaid coherent light beams are a plurality of overlaid coherent laser light beams.

6. The structure according to claim 1, further comprises a transparent layer over the second window layer, wherein the transparent layer is formed after transferring the textured pattern of the photoresist layer to the second window layer, and a material of the transparent layer comprises epoxy.