High output group III nitride light emitting diodes
View Patent ↗A light emitting diode is disclosed that includes a silicon carbide substrate and a light emitting structure formed from the Group III nitride material system on the substrate. The diode has an area greater than 100,000 square microns and has a radiant flux at 20 milliamps current of at least 29 milliwatts at its dominant wavelength between 390 and 540 nanometers.
1. A light emitting diode comprising:
a light emitting layer that comprises a Group III nitride material system;
a first ohmic contact on said light emitting layer;
a silver-based layer between said first ohmic contact and said light emitting layer, said silver-based layer including a first face of said silver-based layer adjacent said first ohmic contact, a second face of said silver-based layer adjacent and directly contacting said light emitting layer and a sidewall of said silver-based layer that extends between said first and second faces;
a barrier layer between said first ohmic contact layer and said silver-based layer and directly contacting said first ohmic contact layer, said barrier layer extending on said first face of said silver-based layer and further extending on said sidewall of said silver-based layer to directly contact said light emitting layer;
a transparent conductive substrate on said light emitting layer opposite said silver-based layer; and
a second ohmic contact directly on said transparent conductive substrate opposite said light emitting layer.
2. A light emitting diode according to claim 1 wherein said transparent conductive substrate comprises a silicon carbide single crystal substrate.
3. A light emitting diode according to claim 2 further comprising a buffer layer between said silicon carbide substrate and said light emitting layer, said buffer layer comprising the Group III nitride material system.
4. A light emitting diode according to claim 3 further comprising at least two layers of opposite conductivity type comprising the Group III nitride material system for providing carriers for recombination and light emission under an applied current.
5. A light emitting diode according to claim 4 wherein said light emitting layer includes at least one layer of indium gallium nitride.
6. A light emitting diode according to claim 2 wherein said silicon carbide substrate is n-type and has a polytype selected from the 3C, 4H, 6H, and 15R polytypes of silicon carbide.
7. A light emitting diode according to claim 1 wherein said light emitting layer comprises a doped semiconductor layer, said silver-based layer is directly on said doped semiconductor layer and said barrier layer is directly on said first face of said silver-based layer and completely encloses said sidewall of said silver-based layer.
8. A light emitting diode according to claim 7 wherein said doped semiconductor layer is a p-type semiconductor layer.
9. A light emitting diode according to claim 1 wherein said transparent conductive substrate includes an oblique sidewall.
10. A light emitting diode according to claim 9 ;
wherein said second ohmic contact is directly on a face of said transparent conductive substrate that is opposite said light emitting layer, and
wherein said second ohmic contact extends on only a first portion of said face and exposes a second portion of said face.