Mk. Kelly et al., Large free-standing GaN substrates by hydride vapor phase epitaxy and laser-induced liftoff, JPN J A P 2, 38(3A), 1999, pp. L217-L219
Free-standing GaN, nearly equal in area to the original 2 inch wafer, was p
roduced from 250-300 mu m thick GaN films grown on sapphire by hydride vapo
r phase epitaxy (HVPE). The thick films were separated from the growth subs
trate by laser-induced liftoff, using a pulsed laser to thermally decompose
a thin layer of GaN at the film-substrate interface. Sequentially scanned
pulses were employed and the liftoff was performed at elevated temperature
(>600 degrees C) to relieve postgrowth bowing. After liftoff, the bow is on
ly slight or absent in the resulting free GaN.