III-nitride light emitting device with reduced strain light emitting layer
View Patent ↗In accordance with embodiments of the invention, strain is reduced in the light emitting layer of a III-nitride device by including a strain-relieved layer in the device. The surface on which the strain-relieved layer is grown is configured such that strain-relieved layer can expand laterally and at least partially relax. In some embodiments of the invention, the strain-relieved layer is grown over a textured semiconductor layer or a mask layer. In some embodiments of the invention, the strain-relieved layer is group of posts of semiconductor material.
1. A device comprising:
a mask layer having a plurality of openings;
a Ill-nitride structure comprising:
a plurality of posts of semiconductor material corresponding to the openings in the mask layer, wherein the plurality of posts are separated by an insulating material, and wherein in a plane parallel to a surface of the mask layer, a lateral extent of a cross section of the plurality of posts is at least 90% of a lateral extent of the device;
a light emitting layer disposed between an n-type region and a p-type region, wherein a major surface of the light emitting layer is substantially parallel to a surface of the mask layer.
2. The device of claim 1 wherein the mask layer comprises silicon and nitrogen.
3. The device of claim 1 wherein each of the posts has a diameter less than 150 nm.
4. The device of claim 1 wherein the light emitting layer is disposed within the posts.
5. The device of claim 1 further comprising a planar layer of p-type semiconductor material disposed over the plurality of posts.
6. The device of claim 1 further comprising a planar layer of n-type semiconductor material disposed over the plurality of posts.
7. The device of claim 1 wherein the posts have a height between 50 nm and 3 μm.
8. The device of claim 1 wherein the insulating material is one of air, a resistive III-nitride material, and an oxide of silicon.
9. The device of claim 1 wherein the posts are truncated polyhedrons.
10. The device of claim 1 wherein the posts are polyhedrons.
11. The device of claim 1 wherein the light emitting layer is a conformal layer formed over the posts.
12. The device of claim 1 wherein:
the light emitting layer has bulk lattice constant a bulk corresponding to a lattice constant of a free standing material of a same composition as the light emitting layer;
the light emitting layer has an in-plane lattice constant a in-plane corresponding to a lattice constant of the light emitting layer as grown in the structure; and
(a in-plane −a bulk )/ a bulk is less than 1%.
13. The device of claim 1 wherein the light emitting layer has a thickness greater than 50 angstroms.
14. The device of claim 1 wherein the light emitting layer is doped with silicon to a dopant concentration between 1×10 18 cm −3 and 1×10 20 cm −3 .
15. The device of claim 1 further comprising:
contacts electrically connected to the n-type region and the p-type region; and
a cover disposed over the III-nitride semiconductor structure.