High efficiency group III nitride LED with lenticular surface
View Patent ↗A light emitting diode is disclosed that includes a conductive substrate, a bonding metal on the conductive substrate and a barrier metal layer on the bonding metal. A mirror layer is encapsulated by the barrier metal layer and is isolated from the bonding metal by the barrier layer. A p-type gallium nitride epitaxial layer is on the encapsulated mirror, an indium gallium nitride active layer is on the p-type layer, and an n-type gallium nitride layer is on the indium gallium nitride layer, and a bond pad is made to the n-type gallium nitride layer.
1. A light emitting diode comprising:
a submount structure;
a bonding metal on said submount structure;
a barrier metal layer on said bonding metal;
an ohmic mirror layer encapsulated by said barrier metal layer;
an epitaxial light emitting region on said encapsulated mirror; and
a lenticular surface at least partially on said epitaxial light emitting region wherein said lenticular surface comprises silicon carbide.
2. A light emitting diode according to claim 1 , said epitaxial light emitting region comprising:
a p-type gallium nitride epitaxial layer;
an indium gallium nitride active layer on said p-type layer;
an n-type gallium nitride layer on said indium gallium nitride layer; and
a bond pad to said n-type gallium nitride layer.
3. A light emitting diode according to claim 1 wherein said ohmic mirror layer comprises a reflective metal layer and an ohmic metal layer.
4. A light emitting diode according to claim 3 wherein said reflective metal layer includes silver and said ohmic metal layer includes platinum.
5. A light emitting diode according to claim 1 comprising a plurality of barrier metal layers on said bonding metal.
6. A light emitting diode according to claim 2 wherein said barrier metal layer is selected from the group consisting of titanium, tungsten, tin and combinations and alloys of these metals.
7. A light emitting diode according to claim 1 wherein said active layer is in a mesa that includes a passivation layer that covers otherwise exposed portions of said mirror, said barrier metal and said bonding metal layer.
8. A light emitting diode according to claim 7 wherein said passivation layer is selected from the group consisting of stoichiometric silicon nitride, non-stoichiometric silicon nitride, and silicon dioxide.
9. A light emitting diode according to claim 1 wherein said bonding metal layer is selected from the group consisting of gold, tin and eutectic mixtures of gold and tin.
10. A light emitting diode according to claim 1 wherein said submount is selected from the group consisting of silicon, silicon carbide, gallium arsenide and copper tungsten.
11. A light emitting diode according to claim 2 wherein said bond pad includes an ohmic contact to said n-type gallium nitride layer.
12. A light emitting diode according to claim 1 further comprising an ohmic contact to said submount.
13. A light emitting diode according to claim 12 having a total dimension between and including said ohmic contacts of no more than 150 microns.
14. A light emitting diode according to claim 1 further comprising a phosphor-containing structure adjacent said n-type gallium nitride layer for converting emissions from said light emitting region into frequencies that will produce white light.
15. A light emitting diode according to claim 10 wherein said submount comprises single crystal silicon carbide and said silicon carbide has a polytype selected from the 3C, 4H, 6H and 15R polytypes of silicon carbide.