Method for the reuse of gallium nitride epitaxial substrates

Patent metadata

Field	Value
Publication number	US-9396943-B2
Application number	US-201514839405-A
Country	US
Kind code	B2
Filing date	Aug 28, 2015
Priority date	Feb 17, 2012
Publication date	Jul 19, 2016
Grant date	Jul 19, 2016

Abstract

A method for the reuse of gallium nitride (GaN) epitaxial substrates uses band-gap-selective photoelectrochemical (PEC) etching to remove one or more epitaxial layers from bulk or free-standing GaN substrates without damaging the substrate, allowing the substrate to be reused for further growth of additional epitaxial layers. The method facilitates a significant cost reduction in device production by permitting the reuse of expensive bulk or free-standing GaN substrates.

First claim

What is claimed is:

1. A method for reusing a III-nitride substrate, comprising:
providing an epitaxy-ready bulk III-nitride substrate that has been previously used to grow a III-nitride optoelectronic or electronic device structure;
growing one or more InGaN sacrificial layers on or above the III-nitride substrate;
growing one or more III-nitride device layers on or above the InGaN sacrificial layers; and
selectively etching the sacrificial layers to separate the III-nitride device layers from the III-nitride substrate without damaging the III-nitride device layers or the III-nitride substrate, such that performance of the III-nitride device layers is not degraded and the III-nitride substrate can be reused.

2. The method of claim 1 , further comprising growing an epitaxial layer on or above the III-nitride substrate, wherein the InGaN sacrificial layers are grown on or above the epitaxial layer.

3. The method of claim 1 , wherein the InGaN sacrificial layers are selectively etched using band-gap-selective photoelectrochemical etching.

4. The method of claim 3 , wherein the band-gap-selective photoelectrochemical etching comprises:
submerging a sample comprised of the III-nitride substrate, InGaN sacrificial layers and III-nitride device layers in an electrolyte solution;
exposing the submerged sample to light that is above the bandgap of the InGaN sacrificial layers, but below the bandgap of the III-nitride substrate or III-nitride device layers, to allow for the etching of the InGaN sacrificial layers, while preventing undesirable etching of the III-nitride substrate or III-nitride device layers.

5. The method of claim 4 , wherein the band-gap-selective photoelectrochemical etching further comprises making contact to an epitaxial layer grown underneath the InGaN sacrificial layers in order to aid in extraction of carriers during the band-gap-selective photoelectrochemical etching.

6. The method of claim 1 , wherein the InGaN sacrificial layers are selectively etched laterally and, after some time, are completely removed, freeing the III-nitride substrate from the III-nitride device layers.

7. The method of claim 1 , wherein an etch is performed to expose the InGaN sacrificial layers before the InGaN sacrificial layers are selectively etched.

8. The method of claim 1 , wherein the selective etching is performed without substantially etching the III-nitride substrate, thereby allowing the III-nitride substrate to be reused for further growth of additional epitaxial layers.

9. The method of claim 1 , wherein the III-nitride device layers are sub-mounted to a carrier substrate before the etch is performed.

10. The method of claim 1 , wherein the performance of the III-nitride device layers is not degraded after the III-nitride device layers are separated from the III-nitride substrate as compared to III-nitride device layers grown on a new or unused III-nitride substrate.

11. The method of claim 1 , wherein the III-nitride substrate is intact and reusable after the III-nitride device layers are separated from the III-nitride substrate.

12. The method of claim 1 , wherein the III-nitride substrate is processed after the III-nitride device layers are separated from the III-nitride substrate to prepare the III-nitride substrate for reuse.

13. The method of claim 12 , wherein the III-nitride substrate is prepared for reuse by planarization techniques.

14. The method of claim 12 , wherein the III-nitride substrate is prepared for reuse by regrowth techniques.

15. A device or substrate processed using the method of claim 1 .

16. A structure, comprising:
an epitaxy-ready bulk III-nitride substrate that has been previously used to grow a III-nitride optoelectronic or electronic device structure;
one or more InGaN sacrificial layers on or above the III-nitride substrate; and
one or more III-nitride device layers on or above the InGaN sacrificial layers;
wherein the InGaN sacrificial layers are selectively etched layers used to separate the III-nitride device layers from the III-nitride substrate without the III-nitride device layers or the III-nitride substrate being damaged, such that performance of the III-nitride device layers is not degraded and the III-nitride substrate can be reused.

Assignees

• Univ California

Inventors

• Holder Casey O
• Feezell Daniel F
• Denbaars Steven P
• Nakamura Shuji

Classifications

• H10P14/36

  characterised by treatments done before the formation of the materials · CPC title

• H10P50/646

  of Group III-V materials · CPC title

• H10P50/617

  of Group III-V materials · CPC title

• H10P14/3416

  Nitrides · CPC title

• H10P14/3216

  Nitrides · CPC title