Biexciton emission from thick ZnSe epilayer grown by molecular beam epitaxy

Photoemission under high photoexcitation in thick ZnSe epilayer grown by molecular beam epitaxy (MBE) has been investigated using time-resolved photoluminescence spectroscopy. The presence of biexcitons is demonstrated under picosecond pulsed excitation as biexciton emission is observed 4 meV below the free exciton emission. The rise time of the biexciton emission follows the rise time of the free exciton and decays with a single exponential form with shorter lifetime than the free exciton. This clear observation of biexciton luminescence in MBE grown ZnSe epilayer, suggests that spontaneous emission commonly observed at lasing threshold under optical pumping at low temperatures is due to biexciton recombination.