Room-temperature stimulated emission of excitons in ZnO/(Mg, Zn)O superlattices

Abstract

We report on the observation of stimulated emission in ${\mathrm{ZnO/Mg}}_x{\mathrm{Zn}}_{\text{1−x}}\mathrm{O}$ superlattices well above room temperature. Two kinds of superlattices grown by laser molecular-beam epitaxy showed clear systematics on the quantum subband levels in absorption and spontaneous emission spectra. Stimulated emission with excitonic origin could be observed at very low optical pumping levels. The threshold excitation intensity changed from 11 to $\text{40\hspace{0.05em}}{\mathrm{kW/cm}}^{\mathrm{2}},$ and the emission energy could be tuned between 3.2 and 3.4 eV, depending on the well thickness and/or the Mg content in the barrier layers. The excitonic stimulated emission could be observed up to 373 K and the characteristic temperature was as high as 87 K.