Well-width dependence of radiative and nonradiative lifetimes in ZnO-based multiple quantum wells

Time-resolved photoluminescence spectroscopy (TRPL) has been employed to study a set of ZnO/Zn 1-x Mg x O (x = 0.12) multiple quantum wells (MQWs) grown by laser molecular beam epitaxy, with well-width L w , varying from 6.91 to 46.5 A. We have estimated the L w dependence of radiative and nonradiative recombination lifetimes of excitons at low temperature (5 K). Radiative recombination lifetimes were dramatically increased at narrow L w , and the thermal release effect of excitonic localization is discussed. On the other hand, the nonradiative recombination rates were almost constant over the L w range studied, so we conclude that suppression of quantum efficiency due to carrier leakage can be avoided even at narrow L w .