Well-width dependence of exciton-phonon coupling strength in ZnO/(Mg,Zn)O multiple quantum wells grown by combinatorial laser molecular beam epitaxy

Excitonic properties of high-quality ZnO/Zn 0.88 Mg 0.12 O multiple quantum wells grown by laser molecular-beam epitaxy were investigated by excitonic absorption spectra taken at temperatures of 5-300 K. Strength of exciton-phonon coupling was deduced from temperature dependence of linewidth of the fundamental excitonic absorption band. Significant reduction of the exciton-phonon coupling with decreasing the well width was observed, which is consistent with the confinement-induced enhancement of the exciton binding energy. The thermal shift of the lowest excitonic energy is independent of well width, suggesting the negligible strain effect characteristically inherent in this material. Growth temperature dependence of third-harmonic generation efficiency in (Ba x Sr 1-x ) 2 CuO 3 alloyed epilayers is reported. It was found that, within the temperature range adopted in this work, the harmonic generation efficiency of the epilayer grown at higher temperature is larger than that grown at low temperature.