Laser annealing of GaN LEDs with reduced pattern effects

• US 9,190,570 B2
• Filed: 11/16/2012
• Issued: 11/17/2015
• Est. Priority Date: 11/06/2009
• Status: Expired due to Fees

• Current Assignee: Ultratech Incorporated (Veeco Instruments Incorporated)
• Original Assignee: Ultratech Incorporated (Veeco Instruments Incorporated)
• Inventors: Hawryluk, Andrew M., Wang, Yun
• Primary Examiner(s): Nguyen, Dao H
• Assistant Examiner(s): Nguyen, Tram H
• Application Number:
  US13/678,946
• Publication Number:
  US 20140131723A1
• Time in Patent Office: 1,096 Days
• Field of Search: 257/76, 257/13, 257/E21.093, 257/192, 257/194, 257E29246-E29253, 257/E21.403, 257/E21.407, 257/20, 257/E21.395, 257/E21.399, 257E29069-E29071, 257/E29.245, 257E49001-E49004, 257/E21.404, 257/40, 257 79-103, 257/918, 257E51018-E51022, 257E33001-E33077, 257/E33.054, 257/E25.028, 257/E25.032, 257/116, 257/117, 257432-437, 257/749, 257E33056-E33059, 257/457, 257/459, 257/E21.077, 257/E21.082, 257/E21.333, 257/E21.12, 257/E21.324, 257/E21.454, 257/E21.497, 257/E33.075, 438/609, 438/167, 438/172, 438 22- 47, 438/69, 438/493, 438/503, 438/507, 438/956, 438/502, 438/509, 438660-664, 438/530, 438/540, 438/550
• US Class Current: 1/1
• CPC Class Codes: H01L 33/0075 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 33/32 containing nitrogen
• CPC Class Codes: H01L 33/38 with a particular shape

Abstract

The disclosure is directed to laser annealing of GaN light-emitting diodes (LEDs) with reduced pattern effects. A method includes forming elongate conductive structures atop either an n-GaN layer or a p-GaN layer of a GaN LED structure, the elongate conductive structures having long and short dimensions, and being spaced apart and substantially aligned in the long dimensions. The method also includes generating a P-polarized anneal laser beam that has an anneal wavelength that is greater than the short dimension. The method also includes irradiating either the n-GaN layer or the p-GaN layer of the GaN LED structure through the conductive structures with the P-polarized anneal laser beam, including directing the anneal laser beam relative to the conductive structures so that the polarization direction is perpendicular to the long dimension of the conductive structures.

Claims

1. A method of laser annealing a GaN light-emitting diode (LED) structure, comprising

forming elongate conductive structures atop either an n-GaN layer or a p-GaN layer of the GaN LED structure, the elongate conductive structures having long and short dimensions, and being spaced apart and substantially aligned in the long dimensions;

generating a P-polarized anneal laser beam that has an anneal wavelength that is greater than the short dimension; and

irradiating either the n-GaN layer or the p-GaN layer of the GaN LED structure through the conductive structures with the P-polarized anneal laser beam, including directing the anneal laser beam relative to the conductive structures so that the polarization direction is perpendicular to the long dimension of the conductive structures.

2. The method of claim 1, wherein the elongate conductive structure has a surface that is generally rectangular.

3. The method of claim 1, wherein the substantial alignment of the elongate conductive structures includes two or more of the elongate conductive structures being parallel.

4. The method of claim 1, wherein the elongate conductive structures define current-spreading electrodes.

5. The method of claim 4, further comprising, after said irradiating, adding at least one contact pad that electrically contacts the current-spreading electrodes.

6. The method of claim 1, wherein the anneal wavelength is about 10.6 microns.

7. The method of claim 1, further comprising scanning with the anneal laser beam over the conductive structures.

8. The method of claim 1, wherein the GaN LED structures are formed on a product substrate and further comprising:

dicing the product substrate to form LED dies from the GaN LED structures.

9. The method of claim 8, further comprising incorporating the LED dies into an LED device structure to form an LED device.

10. A GaN light-emitting diode (LED) apparatus suitable for laser annealing with a P-polarized anneal laser beam having an anneal wavelength, comprising:

a GaN multilayer structure that includes p-GaN and n-GaN layers that sandwich an active layer; and

a plurality of conductive structures formed atop either the p-GaN layer or the n-GaN layer, the conductive structures each being elongate with a long dimension and a short dimension and aligned generally in the same direction, with the short dimension being smaller than the anneal wavelength.

11. The apparatus of claim 10, wherein the elongate conductive structures have a surface that is generally rectangular.

12. The apparatus of claim 10, wherein the substantial alignment of the elongate conductive structures includes two or more of the elongate conductive structures being parallel.

13. The apparatus of claim 10, wherein the elongate conductive structures define current-spreading electrodes.

14. The apparatus of claim 10, wherein the short dimension is smaller than about 10.6 microns.

15. The apparatus of claim 10, wherein the conductive structures are disposed atop the p-GaN layer, and further including a transparent conducting layer between the conductive structures and the p-GaN layer.