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 method of fabricating a light emitting diode (LED) comprising:
growing a light emission region on a first surface of a substrate, the light emission region including an active layer between first and second oppositely doped layers;
creating a moth-eye morphology in at least a portion of a second surface of the substrate;
forming a first contact on the second surface of the substrate and in electrical contact with one of the first or second doped layers; and
forming a second contact in electrical contact with the other of the first or second doped layers.
2. The method of claim 1 wherein the moth-eye morphology is created by reactive ion etching the second surface.
3. The method of claim 1 wherein the moth-eye morphology is created by:
forming a layer on the second surface having a surface morphology; and
etching the layer and underlying second surface to create the moth-eye morphology.
4. The method of claim 3 wherein the layer is formed by:
depositing a substantially uniform layer of material on the second surface; and
forming the surface morphology in the uniform layer.
5. The method of claim 4 wherein the surface morphology is formed in the uniform layer by annealing the uniform layer at a temperature and for a time duration sufficient to form the surface morphology.
6. The method of claim 4 wherein the surface morphology is formed in the uniform layer by:
depositing a mask layer over the uniform layer; and
etching the uniform layer through the mask layer to form the surface morphology.
7. The method of claim 4 wherein the surface morphology is formed in the uniform layer by:
depositing nano-particles over the uniform layer; and
etching the particles and underlying layer to form the surface morphology.
8. The method of claim 3 wherein the layer is formed by depositing a layer of nano-particles on the second surface.
9. The method of claim 3 wherein the layer and second surface are etched using a dry etching process.
10. The method of claim 9 further comprising applying a chemical etch to the second surface after the second surface has been dry etched.
11. The method of claim 9 further comprising annealing the second surface after the second surface has been dry etched.
12. The method of claim 1 wherein the morphology is created using a grit polishing process.
13. A method of fabricating a light emitting diode (LED) comprising:
growing a light emission region on a first surface of a substrate, the light emission region including an active layer between first and second oppositely doped layers;
forming a layer on a second surface of the substrate, the layer having a refractive index substantially the same as the substrate and a moth-eye surface morphology;
forming a first contact on the layer and in electrical contact with one of the first or second doped layers; and
forming a second contact in electrical contact with the other of the first or second doped layers.
14. The method of claim 13 wherein the layer is formed by:
depositing material on the second surface under growth conditions that form the moth-eye surface morphology.
15. The method of claim 13 wherein the layer is formed by:
depositing nano-particles on the second surface, the particles having size, shape and density that form the moth-eye surface; and
mechanically fixing the nano-particles to the second surface.