Activating GaN LEDs by laser spike annealing and flash annealing

• US 8,658,451 B2
• Filed: 07/20/2011
• Issued: 02/25/2014
• 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:
  US13/136,019
• Publication Number:
  US 20110278587A1
• Time in Patent Office: 951 Days
• Field of Search: 257/13, 257/94, 257/76, 257/96, 257/E21.093, 438/22, 438/29, 438/45, 438/47, 438/39, 438/609
• US Class Current: 438/46
• CPC Class Codes: H01L 2933/0016 relating to electrodes
• CPC Class Codes: H01L 33/0095 Post-treatment of devices, e.g. annealing, recrystallisation or short-circuit elimination
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01L 33/42 Transparent materials

Abstract

Methods of performing fast thermal annealing in forming GaN light-emitting diodes (LEDs) are disclosed, as are GaN LEDs formed using fast thermal annealing. An exemplary method includes forming a GaN multilayer structure having a n-GaN layer and a p-GaN layer that sandwich an active layer. The method includes performing fast thermal annealing of the p-GaN layer using either a laser or a flash lamp. 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 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;

performing fast thermal annealing of the p-GaN layer;

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 fast thermal annealing through the transparent conducting layer.

3. The method of claim 2, further comprising performing the fast thermal annealing of the p-contact.

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

10<sup>−

4</sup> ohm-cm² to about 1×

10<sup>−

6</sup> ohm-cm².

5. The method of claim 3, further comprising performing fast thermal annealing of the n-contact.

6. The method of claim 5, 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 fast thermal annealing has a maximum anneal temperature T_AM in the range from about 700°

C. to about 1,500°

C.

8. The method of claim 7, wherein the fast thermal annealing utilizes either a laser or a flash lamp.

9. The method of claim 8, wherein fast thermal annealing is performed with a flash lamp that irradiates the entire p-GaN layer in a single flash.

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

10¹⁷ cm<sup>−

3</sup> to about 5×

10¹⁹ cm<sup>−

3</sup>.

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

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

forming a GaN multilayer structure having a n-GaN layer and a p-GaN layer that sandwich an active layer;

forming a p-contact layer adjacent the p-GaN layer;

forming a n-contact atop the n-GaN layer; and

performing fast thermal annealing of the n-contact.

13. The method of claim 12 where the fast thermal annealing is performed using a laser or a flash lamp.

14. The method of claim 13, wherein the n-contact has a n-contact resistance, and said performing of fast thermal annealing of the n-contact results in the n-contact resistance being in the range from about 1×

10<sup>−

4</sup> ohm-cm² to about 1×

10<sup>−

6</sup> ohm-cm².

15. The method of claim 12, further comprising conducting the fast thermal annealing to have maximum anneal temperature T_AM in the range from about 700°

C. to about 1,500°

C.

16. A GaN light-emitting diode (LED), comprising:

a substrate;

a GaN multilayer structure formed atop the substrate and having a n-GaN layer and a p-GaN layer that sandwich an active layer, wherein the p-GaN layer comprises a fast thermally annealed layer having an activated dopant concentration of greater than about 5×

10¹⁷ cm<sup>−

3</sup> and up to about 5×

10¹⁹ cm<sup>−

3</sup>;

a transparent conducting layer atop the GaN multilayer structure;

a p-contact formed atop the transparent conducting layer; and

a n-contact formed atop an exposed portion of the n-GaN layer.

17. The GaN LED of claim 16, wherein the fast thermally annealed layer is one of a flash lamp fast thermally annealed layer and a laser fast thermally annealed layer.

18. The GaN LED of claim 17, wherein the p-contact has an ohmic contact resistance in the range from about 4×

10<sup>−

4</sup> to about 1×

10<sup>−

6</sup> ohm-cm².

19. The GaN LED of claim 17, wherein the n-contact has an n-contact resistance in the range from about 1×

10<sup>−

4</sup> ohm-cm² to about 1×

10<sup>−

6</sup> ohm-cm².

20. A GaN light-emitting diode (LED), comprising:

a substrate;

a p-contact layer formed atop the substrate;

a GaN multilayer structure formed atop the p-contact layer and having a n-GaN layer and a p-GaN layer that sandwich an active layer, with the p-GaN layer adjacent the p-contact layer, and the n-GaN layer comprising a fast thermally annealed layer having an active dopant concentration of about 3×

10¹⁹ to about 3×

10²¹ cm<sup>−

3</sup>; and

a n-contact formed atop the n-GaN layer.

21. The GaN LED of claim 20, wherein the fast thermally annealed layer is one of a flash lamp fast thermally annealed layer and a laser fast thermally annealed layer.

22. The GaN LED of claim 20, wherein the n-contact has a n-contact resistance in the range from about 1×

10<sup>−

4</sup> ohm-cm² to about 1×

10<sup>−

6</sup> ohm-cm².