Light-emitting device

• US 8,928,022 B2
• Filed: 07/02/2013
• Issued: 01/06/2015
• Est. Priority Date: 10/17/2006
• Status: Active Grant

• Current Assignee: Epistar Corporation
• Original Assignee: Epistar Corporation
• Inventors: Kuo, De-Shan, Tu, Chun-Hsiang, Chiu, Po-Shun, Hsieh, Min-Hsun, Ko, Chun-Teng
• Primary Examiner(s): Bowman, Mary Ellen
• Application Number:
  US13/934,049
• Publication Number:
  US 20130292643A1
• Time in Patent Office: 553 Days
• Field of Search: 257/98, 257/E33.074
• US Class Current: 257/98
• 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 33/382 the electrode extending partially in or entirely through the semiconductor body
• CPC Class Codes: H01L 33/405 Reflective materials
• CPC Class Codes: H01L 33/42 Transparent materials

Abstract

A light-emitting device comprising: a light-emitting stacked layer having a first conductivity type semiconductor layer; a light-emitting layer formed on the first conductivity type semiconductor layer; and a second conductivity type semiconductor layer formed on the light-emitting layer; a transparent conductive oxide layer formed on the second conductivity type semiconductor layer wherein the transparent conductive oxide layer having a first portion and a second portion and the upper surface of the transparent conductive oxide layer is a textured surface; a first electrode formed on the second portion of the transparent conductive oxide layer, and a second electrode formed on the first conductivity type semiconductor layer; a planarization layer formed on the first portion of the transparent conductive oxide layer, and the second electrode; and a reflective layer formed on the planarization layer that is devoid of the first electrode and the second electrode.

Claims

1. A light-emitting device, comprising:

a semiconductor contact layer having a rough top surface, wherein the rough top surface comprises any two adjacent crests having a highest point respectively and a trough having a lowest point between the two adjacent crests; and

a transparent current spreading layer having a top surface on the semiconductor contact layer;

wherein the top surface of the transparent current spreading layer comprises any two adjacent crests having a highest point respectively and a trough having a lowest point between the two adjacent crests;

wherein the rough top surface of the semiconductor contact layer is substantially directly under the top surface of the transparent current spreading layer;

wherein two oblique lines formed by connecting the highest points and the lowest point of the rough top surface on the semiconductor contact layer, and a first angle θ

₁ formed between the two oblique lines;

wherein two oblique lines formed by connecting the highest points and the lowest point of the top surface on the transparent current spreading layer, and a second angle θ

₂ formed between the two oblique lines;

wherein a difference between the first angle θ

₁ and the second angle θ

₂ is not greater than 10 degrees, or the first angle θ

₁ is substantially the same as the second angle θ

₂.

2. The light-emitting device according to claim 1, further comprising a flat region on the trough of the rough top surface of the semiconductor contact layer.

3. The light-emitting device according to claim 2, further comprising a flat region on the trough of the top surface of the transparent current spreading layer.

4. The light-emitting device according to claim 1, wherein a height difference H₁ between the lowest point on the trough of the top surface of the transparent current spreading layer and the lowest point on the trough of the rough top surface of the semiconductor contact layer is greater than 0.

5. The light-emitting device according to claim 4, wherein a height difference H₂ or H₃ between the highest point on the crest of the top surface of the transparent current spreading layer and the highest point on the crest of the rough top surface of the semiconductor contact layer is greater than 0.

6. The light-emitting device according to claim 5, wherein a ratio of the height difference H₁ and the height difference H₂ is between 0.1 and 10.

7. The light-emitting device according to claim 5, wherein a ratio of the height difference H₁ and the height difference H₃ is between 0.1 and 10.

8. The light-emitting device according to claim 1, further comprising a substrate below the semiconductor contact layer.

9. The light-emitting device according to claim 8, further comprising a light-emitting structure between the substrate and the semiconductor contact layer.

10. The light-emitting device according to claim 9, wherein the light-emitting structure comprises a first conductivity type semiconductor layer on the substrate, an active layer on the first conductivity type semiconductor layer, and a second conductivity type semiconductor layer on the active layer.

11. The light-emitting device according to claim 1, wherein a material of the semiconductor contact layer comprises one or more elements selected from a group consisting of gallium, aluminum, indium, arsenic, phosphorous, nitrogen, and silicon.

12. The light-emitting device according to claim 1, wherein the transparent current spreading layer comprises a metal oxide or a metal nitride.

13. The light-emitting device according to claim 8, wherein the substrate is a growth base or a carrier base.

14. The light-emitting device according to claim 8, wherein a material of the light-emitting structure comprises one or more elements selected from a group consisting of gallium, aluminum, indium, arsenic, phosphorous, nitrogen, and silicon.

15. The light-emitting device according to claim 1, wherein the rough top surface of the semiconductor contact layer comprises a cavity shaped as cone or pyramid, wherein the cavity extends from the rough top surface of the semiconductor contact layer downwards to inner of the semiconductor contact layer.