Substrate for growing a III-V light emitting device
View Patent ↗A substrate including a host and a seed layer bonded to the host is provided, then a semiconductor structure including a light emitting layer disposed between an n-type region and a p-type region is grown on the seed layer. In some embodiments, a bonding layer bonds the host to the seed layer. The seed layer may be thinner than a critical thickness for relaxation of strain in the semiconductor structure, such that strain in the semiconductor structure is relieved by dislocations formed in the seed layer, or by gliding between the seed layer and the bonding layer an interface between the two layers. In some embodiments, the host may be separated from the semiconductor structure and seed layer by etching away the bonding layer.
1. A method comprising:
providing a substrate comprising:
a host; and
a seed layer comprising InGaN bonded to the host; and
growing a semiconductor structure on the seed layer, the semiconductor structure comprising a III-nitride light emitting layer disposed between an n-type region and a p-type region, wherein during growth of the semiconductor structure, the seed layer is bonded to the host.
2. The method of claim 1 wherein the substrate further comprises a bonding layer disposed between the host and the seed layer.
3. The method of claim 2 wherein the bonding layer comprises one of an oxide of silicon and a nitride of silicon.
4. The method of claim 1 wherein a coefficient of thermal expansion of the host is at least 90% of a coefficient of thermal expansion of a layer of the semiconductor structure.
5. The method of claim 1 wherein a plurality of trenches are formed in the seed layer, wherein the trenches extend through an entire thickness of the seed layer.
6. The method of claim 5 wherein the plurality of trenches are spaced between 1 micron and 50 microns apart.
7. The method of claim 5 wherein the plurality of trenches are spaced between 50 microns and 2 millimeters apart.
8. The method of claim 5 wherein the substrate further comprises a bonding layer disposed between the host and the seed layer.
9. The method of claim 8 wherein the trenches extend through the seed layer to the bonding layer.
10. The method of claim 5 wherein the trenches extend through the seed layer to the host.
11. The method of claim 5 wherein the difference between a lattice constant of a relaxed, free standing layer having a same composition as the seed layer and a lattice constant of a portion of the semiconductor structure closest to the seed layer is 1% or less.
12. The method of claim 5 wherein the difference between a coefficient of thermal expansion of the seed layer and a coefficient of thermal expansion of the host causes a lattice constant of the seed layer to increase at a growth temperature of a portion of the semiconductor structure such that at a growth temperature, the difference between a lattice constant of the seed layer and a lattice constant of the portion of the semiconductor structure is 1% or less.
13. The method of claim 1 wherein:
the semiconductor structure further comprises a nucleation layer grown directly on the seed layer; and
the difference between a lattice constant of the seed layer and a lattice constant of the nucleation layer is 1% or less.
14. The method of claim 13 wherein the nucleation layer is InGaN.
15. A structure comprising:
a host substrate;
an InGaN seed layer; and
a bonding layer disposed between the InGaN seed layer and the host substrate;
wherein the InGaN seed layer comprises a surface on which III-nitride material can nucleate.
16. The structure of claim 15 wherein the bonding layer is SiO 2 .
17. The structure of claim 15 wherein the host is sapphire.
18. The structure of claim 15 wherein the host is one of Si, SiC, AlN, GaAs, metal, and Y 3 Al 5 O 12 .
19. A method comprising:
providing a substrate comprising:
a host; and
a seed layer bonded to the host; and
growing a semiconductor structure on the seed layer, the semiconductor structure comprising a III-nitride light emitting layer disposed between an n-type region and a p-type region, wherein during growth of the semiconductor structure, the seed layer is bonded to the host; wherein:
a free standing layer of the same composition as the III-nitride light emitting layer has a lattice constant a freestanding ;
the III-nitride light emitting layer has a lattice constant a actual ; and
(|a freestanding −a actual |)/a freestanding is less than 1%.
20. The method of claim 19 wherein the seed layer is InGaN.
21. The method of claim 19 wherein the substrate further comprises a plurality of trenches formed in the seed layer.