Process for making a GaN substrate
View Patent ↗In some embodiments, the invention relates to a process for making a GaN substrate comprising: transferring a first monocrystal GaN layer onto a supporting substrate; applying crystal growth for a second monocrystal GaN layer on the first layer; the first and second GaN layers thereby forming together the GaN substrate, the GaN substrate having a thickness of at least 10 micrometers, and removing at least one portion of the supporting substrate.
1. A method of making a GaN substrate, comprising:
transferring a first monocrystal GaN layer onto a supporting substrate;
growing a second monocrystal GaN layer on the first monocrystal GaN layer, the first and second monocrystal GaN layers together forming the GaN substrate, the GaN substrate having a thickness of at least 10 micrometers; and
removing at least one portion of the supporting substrate.
2. The method of claim 1 , wherein a difference in thermal expansion coefficients of the GaN substrate and the supporting substrate is between about 0.1·10 −6 and about 2·10 −6 K −1 over a range of temperatures extending from about 20° C. to about 500° C.
3. The method of claim 1 , wherein the supporting substrate has at least one surface layer comprising germanium or a III-V semiconductor material.
4. The method of claim 3 , wherein the supporting substrate comprises bulk GaAs.
5. The method of claim 1 , further comprising forming a protective coating on the supporting substrate prior to transferring the first monocrystal GaN layer onto the supporting substrate.
6. The method of claim 5 , wherein the protective coating comprises a dielectric material.
7. The method of claim 5 , wherein the protective coating entirely surrounds the supporting substrate.
8. that the method of claim 7 , wherein removing the at least one portion of the supporting substrate comprises chemically etching the protective coating.
9. The method of claim 5 , wherein forming the protective coating on the supporting substrate comprises forming the protective coating on a face of the supporting substrate to be bonded to the first monocrystal GaN layer.
10. The method of claim 1 , wherein transferring the first monocrystal GaN layer onto the supporting substrate comprises forming a bonding layer on at least one of a bonding surface of the monocrystal GaN layer and a bonding surface of the supporting substrate before contacting the supporting substrate with the first monocrystal GaN layer.
11. The method of claim 10 , wherein the bonding layer comprises SiO 2 or Si 3 N 4 .
12. The method of claim 9 , wherein removing the at least one portion of the supporting substrate comprises chemically etching at least a portion of the protective coating located at an interface between the supporting substrate and the first monocrystal GaN layer.
13. The method of claim 9 , wherein removing the at least one portion of the supporting substrate comprises chemically etching at least one portion of the supporting substrate.
14. The method of claim 13 , wherein chemically etching the at least one portion of the supporting substrate comprises etching the at least one portion of the supporting substrate using aqua regia.
15. The method of claim 13 , wherein chemically etching the at least one portion of the supporting substrate comprises chemically etching the at least one portion of the supporting substrate in an enclosure in which the second monocrystal GaN layer is grown on the first monocrystal GaN layer without handling the supporting substrate between chemically etching the at least one portion of the supporting substrate and growing the second monocrystal GaN layer on the first monocrystal GaN layer.
16. The method of claim 15 , wherein chemically etching the at least one portion of the supporting substrate comprises etching the at least one portion of the supporting substrate using gaseous hydrochloric acid.
17. The method of claim 1 , further comprising epitaxial growth of additional material on the GaN substrate.
18. The method of claim 1 , wherein the first monocrystal GaN layer has a thickness between about 500 angstroms and about 1 micrometer.
19. A method as recited in claim 1 , wherein transferring a first monocrystal GaN layer onto a supporting substrate comprises:
bonding an initial structure comprising the first monocrystal GaN layer to the supporting substrate; and
removing a portion of the initial structure from the first monocrystal GaN layer and leaving the first monocrystal GaN layer on the supporting substrate.
20. The method of claim 19 , further comprising implanting ions into the initial structure and forming an embrittlement area within the initial structure, and wherein removing the portion of the initial structure from the first monocrystal GaN layer comprises imputing energy into the embrittlement area.