We report on the observation of stimulated emission in ZnO/MgxZn1-xO superl
attices well above room temperature. Two kinds of superlattices grown by la
ser 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 40 kW/cm(2), and the
emission energy could be tuned between 3.2 and 3.4 eV, depending on the we
ll thickness and/or the Mg content in the barrier layers. The excitonic sti
mulated emission could be observed up to 373 K and the characteristic tempe
rature was as high as 87 K. (C) 2000 American Institute of Physics. [S0003-
6951(00)04640-4].