Free-standing GaN substrates by hydride vapor phase epitaxy

Thick gallium nitride films 250-350 mum in thickness were grown on 2-inch-d iameter (0001) sapphire wafers by hydride vapor phase epitaxy. The size of the free-standing GaN substrates without cracks separated from the sapphire substrates by laser processing was equal to that of the initial sapphire s ubstrates. The origin of bowing and the broad photoluminescence (PL) spectr a of GaN films was considered the difference in the residual strain between the front and bottom surfaces caused by threading dislocations.