Surface treatment of Si using hydrogen-plasma to improve optoelectronic property of ZnO on (111)Si

Hydrogen-terminated (111)Si was treated by Zn-contained hydrogen plasma at low temperatures ranging from 200–500°C prior to ZnO growth at 400°C by plasma-assisted epitaxy using oxygen gas plasma excited by rf-power at 13.56 MHz. Spot pattern corresponding to c-ZnO surface was observed by reflection high-energy electron diffraction from the layer grown on the Si treated by Zn-contained hydrogen gas plasma at 500°C, in contrast to the ring-pattern from the layers on the Si non-treated or treated at lower temperatures. Optoelectronic property was significantly improved by the surface treatment at 500°C, because the photoluminescence spectra of the ZnO layers grown on the Si treated at 500°C showed strong and sharp bandedge emissions due to bound exciton accompanied with free-exciton emission without significant deep-level emissions at 10 K, while the weak bandedge emissions and green emission due to deep level can be observed from the layers on the substrates non-treated or treated below 400°C in the plasma.