Method for the reuse of gallium nitride epitaxial substrates
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.
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.