Fabrication of nonpolar indium gallium nitride thin films, heterostructures and devices by metalorganic chemical vapor deposition
A method for the fabrication of nonpolar indium gallium nitride (InGaN) films as well as nonpolar InGaN-containing device structures using metalorganic chemical vapor deposition (MOVCD). The method is used to fabricate nonpolar InGaN/GaN violet and near-ultraviolet light emitting diodes and laser diodes.
1. A method of fabricating nonpolar indium gallium nitride (InGaN) based heterostructures and devices, comprising:
(a) providing a smooth, low-defect-density III-nitride substrate or template;
(b) growing one or more nonpolar InGaN layers on the substrate or template;
(c) growing a thin low-temperature nitride capping layer on the nonpolar InGaN layers to prevent In desorption during growth of subsequent layers; and
(d) growing one or more nonpolar n-type and p-type (Al,Ga)N layers at low pressure on the capping layer.
2. The method of claim 1 , wherein the InGaN layers are grown at or near atmospheric pressure.
3. The method of claim 1 , wherein the InGaN layers form one or more quantum well heterostructures.
4. The method of claim 1 , wherein one or more undoped nonpolar GaN barrier layers are grown upon the InGaN layers.
5. The method of claim 4 , wherein the undoped nonpolar GaN barrier layers are grown at or near atmospheric pressure.
6. The method of claim 1 , wherein the capping layer is comprised of GaN.
7. A device fabricated using the method of claim 1 .
8. A method of fabricating nonpolar indium gallium nitride (InGaN) based heterostructures and devices, comprising:
(a) providing a smooth, low-defect-density III-nitride substrate or template;
(b) growing nonpolar InGaN layers on the substrate or template;
(c) growing a thin low-temperature gallium nitride (GaN) capping layer on the nonpolar InGaN layers to prevent In desorption during growth of a p-type GaN layer;
(d) growing one or more InGaN/GaN multiple quantum wells (MQWs) near or at atmospheric pressure on the GaN capping layer;
(e) growing an undoped GaN barrier near or at atmospheric pressure on the InGaN/GaN MQWs; and
(f) growing one or more n-type and p-type (Al,Ga)N layers at low pressure on the undoped GaN barrier.
9. The method of claim 8 , wherein the smooth, low-defect-density III-nitride substrate or template is a GaN, aluminum nitride (AlN) or aluminum gallium nitride (AlGaN) substrate.
10. The method of claim 8 , wherein the substrate comprises a low-defect-density free-standing a-plane GaN wafer, a low-defect-density free-standing m-plane GaN wafer, a low-defect-density free-standing a-plane AlN wafer, a low-defect-density free-standing m-plane AlN wafer, a low-defect-density bulk a-plane GaN wafer, a low-defect-density bulk m-plane GaN wafer, a low-defect-density bulk a-plane AlN wafer, or a low-defect-density bulk m-plane AlN wafer.
11. The method of claim 8 , wherein the template is grown by hydride vapor phase epitaxy (HVPE).
12. The method of claim 11 , wherein the template comprises a low-defect-density hydride vapor phase epitaxy (HVPE) lateral epitaxial overgrown (LEO) a-plane or m-plane GaN template.
13. The method of claim 8 , wherein the template comprises a planar nonpolar a-plane GaN template grown by metalorganic chemical vapor deposition (MOCVD).
14. The method of claim 13 , wherein the a-plane GaN template is grown on an r-plane sapphire substrate by a two-step process that includes a low temperature GaN nucleation layer step and a high temperature GaN growth step.
15. The method of claim 8 , wherein the growing step (b) comprises growing nonpolar InGaN layers on the substrate or template at a reduced temperature below approximately 900° C.
16. The method of claim 8 , wherein the growing step (b) further comprises using an N 2 carrier gas to enhance indium (In) incorporation and decrease In desorption in the nonpolar InGaN layers.
17. The method of claim 8 , wherein the growing step (b) comprises growing nonpolar InGaN layers on the substrate or template near or at approximately atmospheric pressure to enhance InGaN film quality and decrease carbon incorporation.
18. The method of claim 8 , wherein the InGaN/GaN MQWs are grown near or at approximately 600–850 Torr.
19. The method of claim 8 , wherein the n-type and p-type (Al,Ga)N layers, other than the capping layer and barrier layer, are grown near or at approximately 20–150 Torr.
20. A device fabricated using the method of claim 8 .