Thin-film LED with P and N contacts electrically isolated from the substrate
View Patent ↗A thin-film LED includes an insulating substrate, an electrode on the insulating substrate, and an epitaxial structure on the electrode.
1. A method of manufacturing a thin-film light emitting diode, comprising:
forming an epitaxial structure on a growth substrate, the epitaxial structure comprising a first epitaxial layer, a second epitaxial layer, and an active region between the first epitaxial layer and the second epitaxial layer;
forming a reflective electrode layer on the second epitaxial layer of the epitaxial structure;
attaching a substrate with a conductive adhesive layer to the reflective electrode layer such that the reflective electrode layer and the conductive adhesive layer together form a metallic current spreading layer;
removing the growth substrate;
removing part of the epitaxial structure so as to expose a surface of the metallic current spreading layer and a side wall of the first epitaxial layer, the active region and the second epitaxial layer to form a mesa with the epitaxial structure and the metallic current spreading layer, after removing the growth substrate; and
forming a pad contact on the exposed surface of the metallic current spreading layer for a bonding wire.
2. The method of claim 1 , wherein the substrate is an insulating substrate.
3. The method of claim 1 , wherein the substrate is a conductive substrate and an insulating dielectric film layer is formed between the substrate and the conductive adhesive layer.
4. The method of claim 1 , further comprising roughening a surface of the first epitaxial layer to form micro-structures on the surface, the micro-structures being between about 100 nm and 500 nm in size.
5. The method of claim 1 , further comprising forming a metal layer on a bottom surface of the substrate.
6. The method of claim 1 , further comprising:
forming an insulating dielectric film layer on a bottom surface of the substrate; and
forming a metal layer on the insulating dielectric film layer.
7. The method of claim 1 , further comprising:
forming a patterned second electrode on the surface of the first epitaxial layer; and
forming a metal contact on the metallic current spreading layer.
8. The method of claim 7 , wherein the epitaxial structure is etched to expose the reflective electrode layer and the metal contact is formed on the reflective electrode layer.
9. The method of claim 3 , further comprising:
removing part of the metallic current spreading layer from the exposed surface of the metallic current spreading layer so as to expose a surface of the insulating dielectric film layer; and
singulating the thin-film light emitting diode from the exposed surface of the insulating dielectric film layer.
10. The method of claim 1 , wherein the metallic current spreading layer has a thickness greater than about 1 μm.
11. The method of claim 1 , wherein the pad contact is formed directly on the exposed surface of the metallic current spreading layer.
12. The method of claim 1 , further comprising:
forming a patterned second electrode on a top surface of the mesa.
13. The method of claim 1 , wherein the substrate is transparent for the wavelengths between about 300 nm and 700 nm with a transmittance greater than about 50%.
14. The method of claim 1 , wherein the substrate is reflective for the wavelength between about 300 nm and 700 nm with a reflectance greater than about 50%.
15. The method of claim 1 , wherein the first epitaxial layer is an n-type GaN-based layer and the second epitaxial layer is a p-type GaN-based layer.