LED with substrate modifications for enhanced light extraction and method of making same
View Patent ↗The surface morphology of an LED light emitting surface is changed by applying processes, such as a reactive ion etch (RIE) process to the light emitting surface. In one embodiment, the changed surface morphology takes the form of a moth-eye surface. The surface morphology created by the RIE process may be emulated using different combinations of non-RIE processes such as grit sanding and deposition of a roughened layer of material or particles followed by dry etching.
1. A light emitting diode (LED) comprising:
a conductive substrate having a first surface and a second surface, a portion of the first surface having a moth-eye morphology formed in said substrate by a maskless etching process;
a light emission region on the second surface, the light emission region including an active layer between first and second oppositely doped layers;
a first contact on the first surface and in contact with one of the first or second doped layers;
a second contact in contact with the other of the first or second doped layers; and
a current spreading structure in contact with the portion of the first surface having the moth-eye morphology and the first contact.
2. The LED of claim 1 further comprising a substantially smooth region on the first surface, wherein the first contact is on the smooth region.
3. The LED of claim 1 wherein the current spreading structure comprises:
at least one conductive element on the first surface in contact with the first contact.
4. The LED of claim 1 wherein the current spreading structure comprises:
a substantially smooth region on the first surface; and
a conductive element on the smooth region and in contact with the first contact.
5. The LED of claim 1 wherein the current spreading structure comprises a transparent conducting layer on at least a portion of the first surface.
6. The LED of claim 5 wherein the transparent conducting layer is metallic.
7. The LED of claim 5 wherein the transparent conducting layer is doped semiconductor material.
8. The LED of claim 7 wherein the doped semiconductor material is part of the substrate.
9. A light emitting diode (LED) comprising:
a conductive substrate having a nonporous first surface and a second surface, a portion of the first surface having a moth-eye morphology formed in said substrate by a maskless etching process;
a light emission region on the second surface, the light emission region including an active layer between first and second oppositely doped layers;
a first contact on the portion of the first surface having the moth-eye morphology and in contact with one of the first or second doped layers; and
a second contact in contact with the other of the first or second doped layers.