Large Free-Standing GaN Substrates by Hydride Vapor Phase Epitaxy and Laser-Induced Liftoff

Free-standing GaN, nearly equal in area to the original 2 inch wafer, was produced from 250–300 µm thick GaN films grown on sapphire by hydride vapor phase epitaxy (HVPE). The thick films were separated from the growth substrate 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°C) to relieve postgrowth bowing. After liftoff, the bow is only slight or absent in the resulting free GaN.