Spontaneous and stimulated emission of ZnO/Zn0.85Mg0.15O asymmetric double quantum wells

ZnO/Zn0.85Mg0.15O asymmetric double quantum wells (ADQWs) were fabricated on an mm-plane Al2O3 substrate by plasma-assisted molecular beam epitaxy (P-MBE). The ADQW structures were confirmed by comparing the photoluminescence (PL) spectra of the ZnO/Zn0.85Mg0.15O MQWs and ZnO/Zn0.85Mg0.15O ADQWs. The exciton tunnelling properties of the ADQWs were studied by means of temperature-dependent PL spectra. The carrier tunneling through the thin barrier is conducive to stimulated emission in the wide wells (WWs) of the ADQWs. The origin of the stimulated emission is exciton–exciton scattering in the WWs of ADQWs.