Free-standing GaN substrates of up to 2″ diameter can be produced by delamination of thick HVPE (hydride vapour phase epitaxy) films from sapphire with a laser-induced liftoff process. Homoepitaxial films of up to 2 μm thickness were grown on the Ga-face and N-face of these substrates with a low-pressure MOCVD system. The pre-overgrowth polishing of the substrates influences the final surface morphology and growth modus, which also depend on the crystal polarity. PL spectra resolve the bound and free exciton peaks from the overgrown GaN.
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Miskys et al. (1999) studied this question.
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