Group III nitride LED with silicon carbide cladding layer
View Patent ↗A semiconductor structure for light emitting devices includes a Group III nitride active layer positioned between a silicon carbide cladding layer and a Group III nitride cladding layer, wherein the silicon carbide cladding layer and the Group III nitride cladding layer have opposite conductivity types. Moreover, the silicon carbide cladding layer and the Group III nitride cladding layer have respective bandgaps that are larger than the bandgap of the active layer.
1. A light emitting device comprising:
a silicon carbide substrate;
a cladding layer consisting essentially of an epitaxial layer of silicon carbide on said substrate;
a Group III nitride cladding layer of Al x In y Ga 1-x-y N, where 0<x<1 and 0≦y<1 and (x+y)<1;
an active layer of Al x In y Ga 1-x-y N, where 0≦x<1 and 0<y≦1 and (x+y)≦1, said active layer having a first surface and a second surface, said first surface of said active layer being in contact with said silicon carbide cladding layer and said second surface of said active layer being in contact with said Group III nitride cladding layer;
wherein the molar fraction of aluminum in said Group III nitride cladding layer is greater than the molar fraction of aluminum in said active layer;
wherein said silicon carbide cladding layer and said Group III nitride cladding layer have respective bandgaps that are larger than the bandgap of said active layer; and
wherein said silicon carbide substrate, said silicon carbide cladding layer, and said active layer are doped layers of the same conductivity type, and said Group III nitride cladding layer is doped to the opposite conductivity type.
2. A light emitting device according to claim 1 , wherein said active layer and said cladding layers form a double heterostructure.
3. A light emitting device according to claim 1 , wherein said active layer and said cladding layers form a quantum well.
4. A light emitting device according to claim 3 comprising a single quantum well.
5. A light emitting device according to claim 3 comprising a multiple quantum well.
6. A light emitting device according to claim 1 , wherein said silicon carbide cladding layer is a single crystal with a polytype selected from the group consisting of 2H, 3C, 4H, 6H, and 15R.
7. A light emitting device according to claim 1 , further comprising:
a first ohmic contact, wherein said silicon carbide cladding layer is positioned between said first ohmic contact and said active layer; and
a second ohmic contact, wherein said Group III nitride cladding layer is positioned between said second ohmic contact and said active layer.
8. A light emitting device according to claim 7 , wherein:
said first ohmic contact is in contact with said silicon carbide cladding layer, opposite said active layer; and
said second ohmic contact is in contact with said Group III nitride cladding layer, opposite said active layer.
9. A light emitting device according to claim 7 , wherein said first and second ohmic contacts comprise at least one metal selected from the group consisting of aluminum, nickel, titanium, gold, platinum, and vanadium, and layers, alloys, and blends thereof.
10. A light emitting device according to claim 1 , further comprising a p-type contact layer of a Group III nitride, wherein said Group III nitride cladding layer is positioned between said p-type contact layer and said active layer.
11. A light emitting device according to claim 10 , wherein said p-type contact layer is in contact with said Group III nitride cladding layer, opposite said active layer.
12. A light emitting device according to claim 10 , wherein said p-type contact layer is magnesium-doped gallium nitride.
13. A light emitting device according to claim 10 , wherein said p-type contact layer is Al x In 1-x N where 0<x<1.
14. A light emitting device according to claim 10 , wherein said p-type contact layer is In x Ga 1-x N, where 0<x<1.
15. A light emitting device according to claim 10 , wherein said p-type contact layer is selected from the group consisting of indium nitride, aluminum gallium nitride of the formula Al x Ga 1-x N, where 0<x<1, and Al x In y Ga 1-x-y N, where 0<x<1 and 0<y<1 and (x+y)<1.
16. A light emitting device according to claim 10 , wherein said p-type contact layer comprises a superlattice formed from a plurality of Group III nitride layers selected from the group consisting of gallium nitride, indium nitride, Al x In 1-x N, where 0<x<1, Al x Ga 1-x N, where 0<x<1, In x Ga 1-x N, where 0<x<1, and Al x In y Ga 1-x-y N, where 0<x<1 and 0<y<1 and (x+y)<1.
17. A light emitting device according to claim 16 , wherein said superlattice is formed from alternating layers of two Group III nitride layers selected from the group consisting of gallium nitride, indium nitride, Al x In 1-x N, where 0<x<1, Al x Ga 1-x N, where 0<x<1, In x Ga 1-x N, where 0<x<1, and Al x In y Ga 1-x-y N, where 0<x<1 and 0<y<1 and (x+y)<1.