Laser spike annealing for GaN LEDs

• US 8,592,309 B2
• Filed: 11/06/2009
• Issued: 11/26/2013
• Est. Priority Date: 11/06/2009
• Status: Active Grant

• Current Assignee: Veeco Instruments Incorporated
• Original Assignee: Ultratech Incorporated (Veeco Instruments Incorporated)
• Inventors: Wang, Yun, Hawryluk, Andrew M.
• Primary Examiner(s): LAURENZI, MARK A
• Application Number:
  US12/590,360
• Publication Number:
  US 20110108796A1
• Time in Patent Office: 1,481 Days
• Field of Search: 257/13, 257/99, 257/184, 257/76, 257/94, 257/101, 257/103, 257/E33.008, 257/E33.025, 438/37, 438/507, 438/29, 438/47, 438/609
• US Class Current: 438/663
• CPC Class Codes: H01L 33/007 comprising nitride compounds
• CPC Class Codes: H01L 33/0095 Post-treatment of devices, e.g. annealing, recrystallisation or short-circuit elimination
• CPC Class Codes: H01L 33/025 Physical imperfections, e.g. particular concentration or distribution of impurities
• CPC Class Codes: H01L 33/42 Transparent materials

Abstract

Methods of performing laser spike annealing (LSA) in forming gallium nitride (GaN) light-emitting diodes (LEDs) as well as GaN LEDs formed using LSA are disclosed. An exemplary method includes forming atop a substrate a GaN multilayer structure having a n-GaN layer and a p-GaN layer that sandwich an active layer. The method also includes performing LSA by scanning a laser beam over the p-GaN layer. The method further includes forming a transparent conducting layer atop the GaN multilayer structure, and adding a p-contact to the transparent conducting layer and a n-contact to the n-GaN layer. The resultant GaN LEDs have enhanced output power, lower turn-on voltage and reduced series resistance.

Claims

1. A method of forming a gallium nitride (GaN) light-emitting diode (LED), comprising:

forming atop a substrate a GaN multilayer structure having a n-GaN layer and a p-GaN layer that sandwich an active layer, wherein the p-GaN layer includes dopants bound to hydrogen;

performing laser spike annealing (LSA) through at least the p-GaN layer by scanning a laser beam over the p-GaN layer, thereby breaking the hydrogen bonds and activating the dopants therein;

forming a transparent conducting layer atop the GaN multilayer structure; and

adding a p-contact to the transparent conducting layer and a n-contact to the n-GaN layer.

2. The method of claim 1, further comprising performing the LSA through the transparent conducting layer.

3. The method of claim 2, further comprising performing LSA of the p-contact.

4. The method of claim 3, further comprising performing LSA of the n-contact.

5. The method of claim 3, wherein the p-contact has a p-contact resistance, and said performing of LSA of the p-contact results in the p-contact resistance being in a range from about 4×

10<sup>−

4</sup> ohm-cm² to about 1×

10<sup>−

5</sup> ohm-cm².

6. The method of claim 4, further comprising:

forming a ledge in the GaN multilayer structure and transparent conducting layer to expose the n-GaN layer; and

forming the n-contact on the exposed GaN layer.

7. The method of claim 1, wherein the LSA has a maximum anneal temperature T_AM in the range from about 900°

C. to about 1,500°

C.

8. The method of claim 7, wherein the scanning of the laser beam is conducted so that the laser beam has a dwell time from about 10 μ

s to about 10 ms.

9. The method of claim 7, wherein the laser beam has a line-type beam shape with an aspect ratio of about 100:

1.

10. The method of claim 1, wherein the p-GaN layer has an activated dopant concentration after LSA in the range from about 5×

10¹⁷ cm<sup>−

3</sup> to about 5×

10¹⁸ cm<sup>−

3</sup>.

11. The method of claim 1, further comprising forming the active layer to comprise a multiple quantum well structure.

12. The method of claim 1, wherein the dopants consist of Mg.

13. The method of claim 1, wherein the transparent contact layer includes indium tin oxide (ITO).

14. The method of claim 1, wherein the n-contact includes at least one of Ti/Au, Ni/Au or Ti/Al.

15. The method of claim 1, wherein the p-contact includes at least one of Ni/Au and Cr/Au.

16. The method of claim 1, wherein the p-GaN layer has a contact resistance, and wherein the total contact resistance is reduced by about 60% by performing said laser spike annealing.

17. The method of claim 1, wherein the laser spike annealing reaches through the GaN multilayer structure.