CONTACT FOR A SEMICONDUCTOR LIGHT EMITTING DEVICE
Embodiments of the invention include a semiconductor structure comprising a III-nitride light emitting layer disposed between an n-type region and a p-type region. A contact disposed on the p-type region includes a transparent conductive material in direct contact with the p-type region, a reflective metal layer, and a transparent insulating material disposed between the transparent conductive layer and the reflective metal layer. In a plurality of openings in the transparent insulating material, the transparent conductive material is in direct contact with the reflective metal layer.
1 . A device comprising:
a semiconductor structure comprising a III-nitride light emitting layer disposed between an n-type region and a p-type region;
a contact disposed on the p-type region, the contact comprising:
a transparent conductive material in direct contact with the p-type region;
a reflective metal layer;
an transparent insulating material disposed between the transparent conductive layer and the reflective metal layer; and
a plurality of openings in the transparent insulating material, wherein the transparent conductive material is in direct contact with the reflective metal layer in the plurality of openings.
2 . The device of claim 1 wherein the transparent conductive material is one of silver and aluminum.
3 . The device of claim 2 wherein the transparent conductive material comprises a plurality of discrete regions that occupy less than 10% of an area of a surface of the p-type region on which the contact is disposed.
4 . The device of claim 1 wherein the transparent conductive material has a thickness between 0.5 and 10 nanometers.
5 . The device of claim 1 wherein the transparent conductive material is an oxide and has a thickness between 30 and 1000 nanometers.
6 . The device of claim 1 wherein the transparent conductive material is one of indium tin oxide, nickel oxide, and ZnO.
7 . The device of claim 1 wherein the transparent insulating material is one of SiO x , SiN x , MgF 2 , and Al 2 O 3 .
8 . The device of claim 1 wherein the transparent insulating material has a thickness between 200 and 500 nm.
9 . The device of claim 1 wherein the openings have a width between two and fifteen microns.
10 . The device of claim 1 wherein the openings are spaced between 20 and 200 microns apart.
11 . The device of claim 1 wherein the transparent insulating material comprises a multi-layer stack.
12 . The device of claim 11 wherein:
a first layer in the multi-layer stack is in direct contact with the transparent conductive material;
a second layer in the multi-layer stack is in direct contact with the reflective metal layer; and
a third layer disposed between the first and second layers has a lower index of refraction than the first and second layers.
13 . The device of claim 1 wherein the reflective metal layer comprises silver.
14 . The device of claim 1 wherein a surface of the p-type region in direct contact with the transparent conductive material is rough.
15 . The device of claim 1 wherein the openings extend into the transparent conductive material.
16 . The device of claim 1 wherein the openings have a sidewall angle between 5 and 50 degrees with respect to a normal to a top surface of the reflective metal layer.
17 . The device of claim 1 wherein at least one of the transparent insulating material and the transparent conductive material is porous.