Optical pumped stimulated emission in ZnO-based quantum wells grown by PLD

Two series of Mg x Zn 1-x O/ZnO multiple quantum wells with 18 at.% and 27 at.% of magnesium content in barrier layers and well width L w from 1 nm to 20 have been grown by pulsed laser deposition method. The stimulated emission is observed in photoluminescence spectra excited by pulsed laser (λ exc =248 nm). The pump density threshold of stimulated emission nonmonotonously depends on the well width that is associated with an increase of the internal quantum efficiency of two-dimensional structures caused by a reduction of radiative lifetime of excitons at decreasing of the well width as it has been shown by the time-resolved photoluminescence spectra analysis. The minimum value of a lifetime τ r =355 ps was obtained for the Mg 0.27 Zn 0.73O /ZnO MQW with the well width L w =2.6 nm.