Room-temperature stimulated emission from ZnO multiple quantum wells   grown on lattice-matched substrates
  The optical properties of ZnO quantum wells, which have potential application of short-wavelength semiconductor laser utilizing a high-density excitonic effect, were investigated. Stimulated emission of excitons was observed at temperatures well above room temperature due to the adoption of the lattice-matched substrates. The mechanism of stimulated emission from ZnO quantum wells is discussed in this chapter. 
T. Makino, Y. Segawa, M. Kawasaki, and H. Koinuma