Vertical III-nitride thin-film power diode
A vertical III-nitride thin-film power diode can hold off high voltages (kV's) when operated under reverse bias. The III-nitride device layers can be grown on a wider bandgap template layer and growth substrate, which can be removed by laser lift-off of the epitaxial device layers grown thereon.
1. A method for fabricating a vertical III-nitride thin-film power diode, comprising:
providing a growth substrate having a bandgap;
a growing a template layer on the growth substrate;
growing a high-doped n-type AlGaN bottom layer on the template layer, wherein the high-doped n-type AlGaN bottom layer has a smaller bandgap energy than the bandgap energies of the template layer and the growth substrate;
growing a low-doped n-type AlGaN drift layer on the high-doped n-type AlGaN bottom layer;
growing a top contact on the low-doped n-type AlGaN drift layer;
bonding a host substrate to the top contact; and
exposing the high-doped n-type AlGaN bottom layer through the growth substrate and the template layer to a light source having energy greater than the bandgap energy of the high-doped n-type AlGaN bottom layer but less than the bandgap energies of the template layer and the growth substrate, thereby causing the high-doped n-type AlGaN bottom layer to heat and separate from the template layer and growth substrate due to a difference in thermal expansion.
2. The method of claim 1 , wherein the high-doped n-type AlGaN bottom layer has an Al composition less than 60%.
3. The method of claim 2 , wherein the light source comprises a laser having a wavelength of 248 nm or less.
4. The method of claim 1 , wherein the high-doped n-type AlGaN bottom layer has an Al composition greater than 60%.
5. The method of claim 4 , wherein the light source comprises a laser having a wavelength of 193 nm or less.
6. The method of claim 1 , further comprising growing an ohmic contact on the high-doped n-type AlGaN bottom layer that is exposed after separation of the template layer and the growth substrate.
7. The method of claim 6 , wherein the ohmic contact comprises Ti or Al.
8. The method of claim 1 , wherein the top contact comprises a high-doped p-type III-nitride top layer on the low-doped n-type AlGaN drift layer, an ohmic contact on the high-doped p-type III-nitride top layer, and a dielectric layer outside the ohmic contact.
9. The method of claim 8 , wherein the high-doped p-type III-nitride top layer comprises AlGaN or GaN.
10. The method of claim 8 , wherein the ohmic contact comprises Ni, Pd, or Pt.
11. The method of claim 8 , wherein the dielectric layer comprises SiN, SiO 2 , SiON, or Al 2 O 3 .
12. The method of claim 1 , wherein the top contact comprises a Schottky contact on the low-doped n-type AlGaN drift layer and a dielectric layer outside the Schottky contact.
13. The method of claim 12 , wherein the Schottky contact comprises Ni, Pd, Pt, Mo, Rh, Au, Ru, or W.
14. The method of claim 12 , wherein the dielectric layer comprises SiN, SiO 2 , SiON, or Al 2 O 3 .
15. The method of claim 1 , wherein the doping of the low-doped n-type AlGaN drift layer is less than 1×10 16 /cm 3 .
16. The method of claim 15 , wherein the dopant of the low-doped n-type AlGaN drift layer is Si.
17. The method of claim 1 , wherein the thickness of the low-doped n-type AlGaN drift layer is greater than 4 μm.
18. The method of claim 1 , wherein the growth substrate comprises Al 2 O 3 or AlN.
19. The method of claim 1 , wherein the template layer comprises AlN or AlGaN.
20. The method of claim 19 , where in the template layer has an Al composition greater than the high-doped n-type AlGaN bottom layer.
21. The method of claim 1 , wherein the top layer further comprises an edge termination structure.
22. The method of claim 21 , wherein the edge termination structure comprises a guard ring or a junction termination extension.
23. The method of claim 1 , wherein the host substrate comprises CuW or GaAs.
24. The method of claim 1 , wherein the bonding comprises bonding a bond metal to the host substrate and the top contact and melting the bond metal.
25. The method of claim 24 , wherein the bond metal comprises two or more metals that form a eutectic.
26. The method of claim 24 , wherein the bond metal comprises InPd.