LIGHT EMITTING DIODE ARRAY AND METHOD FOR MANUFACTURING THE SAME

• US 20130032815A1
• Filed: 03/16/2012
• Published: 02/07/2013
• Est. Priority Date: 08/05/2011
• Status: Active Grant

• Current Assignee: Advanced Optoelectronic Technology, Inc.
• Original Assignee: Advanced Optoelectronic Technology, Inc.
• Inventors: HUNG, TZU-CHIEN, SHEN, CHIA-HUI
• Granted Patent: US 9,190,451 B2
• Time in Patent Office: Days
• US Class Current: 257/76
• CPC Class Codes: H01L 27/156 two-dimensional arrays
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 33/10 with a light reflecting structure, e.g. semiconductor Bragg reflector
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers
• CPC Class Codes: H01L 33/62 Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls

Abstract

An LED array includes a substrate, protrusions formed on a top surface of the substrate, and LEDs formed on the top surface of the substrate and located at a top of the protrusions. The LEDs are electrically connected with each other. Each LED includes a connecting layer, an n-type GaN layer, an active layer, and a p-type GaN layer formed on a top of the protrusions in sequence. A bottom surface of the n-type GaN layer connecting the connecting layer has a roughened exposed portion. The bottom surface of the n-type GaN layer has an N-face polarity.

Claims

1. An LED array comprising:

a substrate;

a plurality of protrusions formed on a top surface of the substrate; and

a plurality of LEDs formed on the top surface of the substrate and located at a top of the protrusions, the LEDs being in electrical connection with each other, each LED comprising a connecting layer, an n-type GaN layer, an active layer, and a p-type GaN layer formed on a top of the protrusions in sequence, a bottom surface of the n-type GaN layer connecting the connecting layer having a roughened exposed portion, the bottom surface of the n-type GaN layer having an N-face polarity.

2. The LED array as claimed in claim 1, wherein the protrusions are spaced from each other and reflect light emitted from the active layer toward a light emitting face of the LED.

3. The LED array as claimed in claim 2, wherein each protrusion is a hemisphere.

4. The LED array as claimed in claim 1, wherein grooves are defined between the LEDs to separate the LEDs from each other, and the grooves extend through the connecting layer, the n-type GaN layer, the active layer, and the p-type GaN layer to expose the protrusions.

5. The LED array as claimed in claim 4, wherein wires are located at the grooves and electrically connect LEDs, the wires covering some of the protrusions.

6. The LED array as claimed in claim 5, wherein insulating layers are formed in the grooves, and the wires are formed on the insulating layers.

7. The LED array as claimed in claim 1, wherein a buffer layer and a GaN layer are formed on the top surface of the substrate in sequence, the protrusions are received in a bottom end of the buffer layer, and the LEDs are formed on a top surface of the GaN layer.

8. The LED array as claimed in claim 7, wherein the GaN layer is an n-type GaN and the top surface of the GaN layer away from the substrate has a Ga-face polarity.

9. The LED array as claimed in claim 1, wherein the connecting layer is made of a material selected from a group consisting of AlN, SiO₂, and silicon nitride.

10. The LED array as claimed in claim 1, wherein a thickness of the connecting layer is in a range of 5 nm to 1000 nm.

11. The LED array as claimed in claim 1, wherein the n-type GaN layer has a top surface away from the connecting layer, the top surface comprises a first area and a second area, the active layer and the p-type GaN layer are formed on the first area in sequence, a p-type electrode is formed on the p-type GaN layer, and an n-type electrode is formed on the second area.

12. The LED as claimed in claim 11, wherein a transparent conductive layer is disposed between the p-type electrode and the p-type GaN layer.

13. A method for manufacturing an LED array comprising:

providing a substrate;

forming a plurality of protrusions by etching on a top end of the substrate;

forming a connecting layer, an n-type GaN layer, an active layer and a p-type GaN layer at a top of the substrate in sequence, the connecting layer, the n-type GaN layer, the active layer and the p-type GaN layer cooperatively forming a semiconductor structure, a bottom surface of the n-type GaN layer facing towards and in connection with the connecting layer having an N-face polarity;

forming grooves in the semiconductor structure and dividing the semiconductor structure into a plurality of LEDs, the grooves passing through the p-type GaN layer, the active layer and the n-type GaN layer and the connecting layer to expose the protrusions;

etching the connecting layer by alkaline solution to expose a portion of the bottom surface of the n-type GaN layer, and correspondingly roughening the exposed portion of the bottom surface of the n-type GaN layer during the etching; and

forming electrical connections between the LEDs.

14. The method as claimed in claim 13, wherein before the semiconductor structure is formed, a buffer layer and a GaN layer are formed on the substrate in sequence and a surface of the GaN layer away from the substrate has a Ga-face polarity.

15. The method as claimed in claim 13, wherein the alkaline solution is a strong alkaline solution, and the connecting layer and the n-type GaN layer are etched by the strong alkaline solution under a temperature of 85 degrees centigrade for 30 to 60 minutes.

16. The method as claimed in claim 15, wherein the strong alkaline solution is KOH solution or NaOH solution.

17. The method as claimed in claim 13, wherein insulating layers are formed in the grooves before forming electrical connections between the LEDs.

18. The method as claimed in claim 13, wherein the connecting layer is made of a material selected from a group consisting of AlN, SiO₂, and silicon nitride.