Ultra-thin ohmic contacts for p-type nitride light emitting devices
View Patent ↗A flip-chip semiconductor based Light Emitting Device (LED) can include an n-type semiconductor substrate and an n-type GaN epi-layer on the substrate. A p-type GaN epi-layer can be on the n-type GaN epi-layer and a metal ohmic contact p-electrode can be on the p-type GaN epi-layer, where the metal ohmic contact p-electrode can have an average thickness less than about 25 Å. A reflector can be on the metal ohmic contact p-electrode and a metal stack can be on the reflector. An n-electrode can be on the substrate opposite the n-type GaN epi-layer and a bonding pad can be on the n-electrode.
1. A flip-chip semiconductor based Light Emitting Device (LED) comprising:
an n-type GaN epi-layer on a substrate;
a p-type GaN epi-layer on the n-type GaN epi-layer;
a metal ohmic contact on the p-type GaN epi-layer, the metal ohmic contact comprising an average thickness less than about 5 Å and a specific contact resistivity less than about 10 −3 ohm-cm 2 ;
a reflector on the metal ohmic contact; and
a metal stack on the reflector.
2. An LED according to claim 1 wherein the metal ohmic contact covers less than about 67% of the p-type GaN epi-layer.
3. An LED according to claim 1 wherein the metal ohmic contact covers less than about 47% of the p-type GaN epi-layer.
4. An LED according to claim 1 wherein the metal ohmic contact comprises an average thickness less than about 3 Å.
5. An LED according to claim 4 wherein the metal ohmic contact covers less than about 28% of the p-type GaN epi-layer.
6. An LED according to claim 1 wherein the metal ohmic contact comprises an average thickness of about 1 Å.
7. An LED according to claim 6 wherein the metal ohmic contact covers less than about 13% of the p-type GaN layer.
8. An LED according to claim 1 wherein the reflector comprises a thickness greater than about 300 Å.
9. An LED according to claim 8 wherein the reflector comprises aluminum and/or silver.
10. A flip chip semiconductor based LED comprising:
a p-type nitride layer;
a metal ohmic contact on the p-type nitride layer, the metal ohmic contact comprising an average thickness of less than about 5 Å and a specific contact resistivity less than about 10 −3 ohm-cm 2 ; and
a reflector on the metal ohmic contact.
11. An LED according to claim 2 wherein the metal ohmic contact comprises a discontinuous layer on the p-type GaN epi-layer.
12. An LED according to claim 10 wherein the metal ohmic contact covers less than about 67% of the p-type nitride layer.
13. An LED according to claim 12 wherein the metal ohmic contact comprises a discontinuous layer on the p-type nitride layer.
14. An LED according to claim 10 wherein the metal ohmic contact comprises an average thickness less than about 3 Å.
15. A flip chip semiconductor based LED comprising:
a p-type nitride layer;
a metal ohmic contact on the p-type nitride layer, the metal ohmic contact comprising an average thickness of less than about 10 Å wherein the metal ohmic contact covers less than about 67% of the p-type nitride layer and wherein the metal ohmic contact comprises a discontinuous layer on the p-type nitride layer; and
a reflector on the metal ohmic contact.
16. A flip-chip semiconductor based Light Emitting Device (LED) comprising:
an n-type GaN epi-layer on a substrate;
a p-type GaN epi-layer on the n-type GaN epi-layer;
a metal ohmic contact on the p-type GaN epi-layer, the metal ohmic contact comprising an average thickness less than about 10 Å, wherein the metal ohmic contact covers less than about 67% of the p-type GaN epi-layer and wherein the metal ohmic contact comprises a discontinuous layer on the p-type GaN epi-layer;
a reflector on the metal ohmic contact; and
a metal stack on the reflector.