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

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.