Fabrication of freestanding GaN by HVPE and optically pumped stimulated emission at room temperature

Single-crystalline freestanding GaN, having a current maximum size of 10 x 10 mm(2) and a thickness of 350 mu m, was fabricated by hydride vapour phas e epitaxy (HVPE) growth of thick-film GaN on a sapphire substrate and subse quent removal of the host sapphire substrate. We also observed the room-tem perature optically pumped stimulated emission (SE) from a 1 mm width cleave d cavity prepared from freestanding GaN. At a maximum power density of 2 MW cm(-2), the peak energy and FWHM of SE were 3.318 eV and 8 meV, respective ly. The threshold pumping power density for the one set of SE was 0.37 MW c m(-2), and the output becomes highly TE-polarized.