Method of manufacturing low cost, high efficiency LED
A low cost, high efficiency light-emitting diode design is disclosed. In some embodiments, a p-n junction of a light-emitting diode is formed in an epitaxial layer grown on a substrate. Grinding the backside of an associated wafer after encapsulation not only opens a light path for the light emitting diode but removes most residual defects.
1. A method, comprising:
adding doped regions to a top side of an epitaxial layer grown on a substrate that form one or more p-n junctions comprising one or more light-emitting diodes, wherein an anode and a cathode of each light-emitting diode are both situated in the same layer; and
opening a light path for the one or more light-emitting diodes by backgrinding to at least remove the substrate, wherein light is emitted from a bottom side of the epitaxial layer.
2. The method of claim 1 , wherein backgrinding removes a portion of the epitaxial layer.
3. The method of claim 1 , wherein backgrinding removes defects near an interface of the substrate and the epitaxial layer.
4. The method of claim 1 , wherein the emitted light comprises white or colored light.
5. The method of claim 1 , wherein light emission occurs from a diffusion region between p-type and n-type regions comprising each p-n junction.
6. The method of claim 1 , further comprising adding a plurality of metal layers over the doped side of the epitaxial layer.
7. The method of claim 1 , further comprising adding metal connectors comprising a plurality of metal layers that provide electrical connectivity and are reflectors for incident photons.
8. The method of claim 6 , wherein a lower metal layer that is closer to the epitaxial layer is thicker than a higher metal layer.
9. The method of claim 6 , further comprising adding pillars or bumps to the metal layers and attaching to a lead frame.
10. The method of claim 1 , wherein both p-type and n-type metal contacts of a p-n junction comprising each light-emitting diode comprise photonic reflectors.
11. The method of claim 1 , wherein an array of p-type and n-type metal contacts corresponding to an array of p-n junctions comprise photonic reflectors.
12. The method of claim 1 , further comprising overmolding or encapsulating in a semiconductor package.
13. The method of claim 12 , wherein the package comprises a quad-flat no-leads (QFN) package.
14. The method of claim 12 , wherein encapsulating encapsulates the light emitting portions of the one or more light emitting diodes and backgrinding removes at least a portion of the encapsulant before reaching and removing the substrate.
15. The method of claim 1 , further comprising adding a phosphor layer over a portion exposed from backgrinding.
16. The method of claim 15 , wherein the phosphor layer comprises a plastic overlay film with embedded or layered phosphor.
17. The method of claim 15 , wherein the phosphor is patterned to output one or more colors of light.
18. The method of claim 1 , wherein the one or more light-emitting diodes are fabricated via an entirely batch process using standard semiconductor processing techniques.
19. The method of claim 1 , further comprising integrating one or more other electronic devices with the one or more light-emitting diodes.
20. The method of claim 1 , wherein the one or more light emitting diodes are arranged in an array to form a display.