Vertical III-nitride thin-film power diode

• US 9,595,616 B1
• Filed: 12/02/2015
• Issued: 03/14/2017
• Est. Priority Date: 12/02/2015
• Status: Active Grant

• Current Assignee: National Technology & Engineering Solutions Of Sandia LLC (Honeywell International Inc.)
• Original Assignee: Sandia Corporation (Martin Marietta Corporation)
• Inventors: Wierer, Jonathan Jr., Fischer, Arthur J., Allerman, Andrew A.
• Primary Examiner(s): Erdem, Fazli
• Application Number:
  US14/957,012
• Time in Patent Office: 468 Days
• US Class Current: 1/1
• CPC Class Codes: H01L 21/0254 Nitrides
• CPC Class Codes: H01L 21/268 using electromagnetic radiation, e.g. laser radiation
• CPC Class Codes: H01L 29/0615 by the doping profile or the shape or the arrangement of the PN junction, or with supplementary regions, e.g. junction termination extension [JTE] LDD or drain offset regions H01L29/7833
• CPC Class Codes: H01L 29/0619 with a supplementary region doped oppositely to or in rectifying contact with the semiconductor containing or contacting region, e.g. guard rings with PN or Schottky junction
• CPC Class Codes: H01L 29/2003 Nitride compounds
• CPC Class Codes: H01L 29/6609 Diodes
• CPC Class Codes: H01L 29/66204 Diodes
• CPC Class Codes: H01L 29/66212 Schottky diodes
• CPC Class Codes: H01L 29/861 Diodes
• CPC Class Codes: H01L 29/8613 Mesa PN junction diodes
• CPC Class Codes: H01L 29/872 Schottky diodes

Abstract

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.

Claims

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, SiO₂, SiON, or Al₂O₃.

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, SiO₂, SiON, or Al₂O₃.

15. The method of claim 1, wherein the doping of the low-doped n-type AlGaN drift layer is less than 1×

10¹⁶/cm³.

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 μ

m.

18. The method of claim 1, wherein the growth substrate comprises Al₂O₃ 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.