Method of fabricating vertical devices using a metal support film
A method of fabricating semiconductor devices, such as GaN LEDs, on insulating substrates, such as sapphire. Semiconductor layers are produced on the insulating substrate using normal techniques. Trenches that define the boundaries of the individual devices are formed through the semiconductor layers and into the insulating substrate, beneficially by inductive coupled plasma reactive ion etching. A first support structure is attached to the semiconductor layers. The hard substrate is then removed, beneficially by laser lift off. A second supporting structure, preferably conductive, is substituted for the hard substrate and the first supporting structure is removed. Individual devices are then diced, beneficially by etching through the second supporting structure. A protective photo-resist layer can protect the semiconductor layers from the attachment of the first support structure. A conductive bottom contact (possibly reflective) can be inserted between the second supporting structure and the semiconductor layers.
1. A vertical topology light emitting device, comprising:
a conductive support structure;
a conductive adhesion structure comprising a first metallic layer on the conductive support structure and a second metallic layer, the first metallic layer being thicker than the second metallic layer, wherein the first metallic layer comprises a first metal and the second metallic layer comprises a second metal different from the first metal;
a reflective structure on the second metallic layer, the reflective structure also serving as a first electrode, wherein the reflective structure comprises a reflective metal layer and a metal contact directly on a surface of the reflective metal layer, wherein the reflective metal layer is thicker than the metal contact;
a GaN-based semiconductor layer on the metal contact, the GaN-based semiconductor layer comprising an active layer, wherein the active layer comprises InGaN;
wherein the reflective structure reflects light from the active layer, on the surface of the reflective metal layer, wherein the surface of the reflective metal layer is a dominant reflective surface,
a second electrode on a surface of the GaN-based semiconductor layer, the second electrode comprising a first layer and a second layer on the first layer; and
a metal pad on the second electrode,
wherein the reflective structure reflects light from the active layer back through the surface of the GaN-based semiconductor layer.
2. The device of claim 1 , wherein the conductive support structure comprises a metallic support layer.
3. The device of claim 1 , wherein the conductive support structure comprises a thermally conductive material.
4. The device of claim 1 , wherein the conductive support structure comprises an electrically conductive material.
5. The device of claim 1 , wherein the conductive support structure is less than about 100 microns thick.
6. The device of claim 1 , wherein the conductive support structure comprises at least one of Cu, Al, or Au.
7. The device of claim 1 , wherein the conductive adhesion structure comprises at least one of Au or Cr.
8. The device of claim 1 , wherein the first metallic layer contacts the conductive support structure.
9. The device of claim 1 , wherein the second metallic layer contacts the reflective structure.
10. The device of claim 1 , wherein the first metallic layer is located, relative to the second metallic layer, proximate to the conductive support structure.
11. The device of claim 1 , wherein the first metallic layer comprises Au.
12. The device of claim 1 , wherein the second metallic layer comprises Cr.
13. The device of claim 1 , wherein the reflective structure comprises aluminum or titanium.
14. The device of claim 1 , wherein a reflectivity of the reflective metal layer is higher than a reflectivity of the metal contact.
15. The device of claim 1 , wherein the shortest distance from a reflecting surface of the reflective structure to the surface of the GaN-based semiconductor layer is less than 5 microns.
16. The device of claim 1 , wherein the GaN-based semiconductor layer comprises:
a first-type semiconductor layer on the metal contact; and
a second-type semiconductor layer on the first-type semiconductor layer,
wherein the active layer is located between the first-type semiconductor layer and the second-type semiconductor layer.
17. The device of claim 16 , wherein the first-type semiconductor layer is n-type and the second-type semiconductor layer is p-type.
18. The device of claim 1 , wherein the active layer has a composition to emit blue light.
19. The device of claim 1 , wherein the second electrode comprises a second-type contact.
20. The device of claim 1 , wherein the second electrode comprises a transparent contact.
21. The device of claim 20 , wherein the transparent contact comprises at least one of Ru, Ni, Au, and ITO.
22. The device of claim 1 , wherein the first metallic layer of the second electrode comprises Au.
23. The device of claim 1 , wherein the metal pad comprises at least one of Pd, Pt, Au, and Al.
24. The device of claim 1 , wherein the metal pad has a diameter of about 100 microns.
25. The device of claim 1 , wherein the surface of the reflective metal layer is a dominant reflective surface with respect to a surface inside of the reflective metal layer.