LED fabrication via ion implant isolation
View Patent ↗A semiconductor light emitting diode includes a semiconductor substrate, an epitaxial layer of n-type Group III nitride on the substrate, a p-type epitaxial layer of Group III nitride on the n-type epitaxial layer and forming a p-n junction with the n-type layer, and a resistive gallium nitride region on the n-type epitaxial layer and adjacent the p-type epitaxial layer for electrically isolating portions of the p-n junction. A metal contact layer is formed on the p-type epitaxial layer. In method embodiments disclosed, the resistive gallium nitride border is formed by forming an implant mask on the p-type epitaxial region and implanting ions into portions of the p-type epitaxial region to render portions of the p-type epitaxial region semi-insulating. A photoresist mask or a sufficiently thick metal layer may be used as the implant mask.
1. A semiconductor light emitting diode comprising:
a conductive substrate with a metal contact on one face of said substrate;
a first epitaxial region of Group III-nitride on the opposite face of said substrate, said epitaxial region having a first conductivity type;
a second epitaxial region of Group III-nitride on said first epitaxial region, said second epitaxial region having a second conductivity type opposite said first conductivity type;
said first and second epitaxial regions forming a p-n junction therebetween;
a Group III-nitride isolation region on said first epitaxial region and adjacent said second epitaxial region, said Group III-nitride isolation region having an increased resistivity compared to said second epitaxial region;
said Group III nitride isolation regions electrically isolating portions of said p-n junction; and
a lead frame attached to said epitaxial regions of said light emitting diode by a die attach metal for defining a current path through said epitaxial regions and through said conductive substrate to said metal contact on said substrate with said isolation region preventing unwanted metal-semiconductor connections between said lead frame and said p-n junction.
2. A light emitting diode according to claim 1 wherein said isolation region has a resistivity greater than about 2000 Ω-cm.
3. A light emitting diode according to claim 1 wherein said isolation region is semi-insulating.
4. A light emitting diode according to claim 1 , further comprising a metal contact layer on a top surface of said second epitaxial region, wherein said metal contact layer exposes a portion of the top surface of said second epitaxial region.
5. A light emitting diode according to claim 3 , wherein said isolation region lies beneath the exposed portion of the top surface of said second epitaxial region.
6. A light emitting diode according to claim 3 , wherein said metal contact layer comprises an ohmic contact layer.
7. A light emitting diode according to claim 5 , wherein said metal contact layer is selected from the group consisting of reflective layers, bonding layers, and combinations thereof.
8. A light emitting diode according to claim 1 wherein said substrate comprises a material selected from the group consisting of silicon carbide, ZnO, MgO, spinel, silicon, gallium nitride and aluminum nitride.
9. A light emitting diode according to claim 1 wherein said substrate comprises silicon carbide having a polytype selected from the group consisting of the 2H, 4H, 6H, 8H, 15R, and 3C polytypes of silicon carbide.
10. A light emitting diode according to claim 1 wherein said substrate is semi-insulating.
11. A light emitting diode according to claim 1 , further comprising a passivation layer on said epitaxial layers.
12. A light emitting diode according to claim 11 , wherein said passivation layer comprises a material selected from the group consisting of silicon nitride, silicon dioxide and insulating polymers.
13. An LED lamp including the light emitting diode according to claim 1 .