PHOTOLUMINESCENCE AND OPTICAL GAIN IN HIGHLY EXCITED GAN

A systematic study of the near-band-edge photoluminescence of epitaxia lly grown GaN as a function of excitation density has been carried out . While at low densities free and bound-exciton emission lines govern the spectrum, new luminescence bands are detected at densities above 1 MW/cm(2). Gain measurements and temperature-dependent investigations indicate that nonlinear processes like biexciton annihilation, exciton -exciton-scattering and stimulated A-LO-emission are dominant at low t emperatures, while exciton-free-carrier scattering occurs at temperatu res above 200 K.