Fabrication of freestanding 2″-GaN wafers by hydride vapour phase epitaxy and self-separation during cooldown

• Published in: Physica status solidi. A, Applications and materials science Vol. 207; no. 6; pp. 1287 - 1291
• Main Authors: Lipski, Frank, Wunderer, Thomas, Schwaiger, Stephan, Scholz, Ferdinand
• Format: Journal Article
• Language: English
• Published: Berlin WILEY-VCH Verlag 01.06.2010; WILEY‐VCH Verlag; Wiley-VCH
• Subjects: Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; GaN; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; morphology; patterning; Physics; structure; Vapor phase epitaxy; growth from vapor phase; VPE; Template method; Scanning electron microscopy; Optical microscopy; Surface morphology; Wafers; Operating mode; VPE; Photolithography; Masks; Gallium nitride; Deposition process
• ISSN: 1862-6300; 1862-6319
• DOI: 10.1002/pssa.200983517

Using a dielectric mask, structured by optical lithography, freestanding 2″‐GaN wafers were prepared by hydride vapour phase epitaxy (HVPE) and self‐separation during cooldown. The mask was deposited on a GaN template grown on sapphire by metal organic vapour phase epitaxy (MOVPE) and it was shown that the instability of a SiN mask at growth temperature supports the further self‐separation. Testing different mask geometries, a hexagonally shaped pattern with a period of 30 µm and an opening of 3 µm showed best performance. This mask allowed the growth and separation of a full 2″ GaN wafer by utilizing the stress arising during cooldown from thermal mismatch to the substrate. Thickness inhomogenity was below 10% and the samples show good surface morphology.