H2O-VAPOR-ACTIVATED ZnO GROWTH ON A-FACE SAPPHIRE SUBSTRATES BY METALORGANIC MOLECULAR-BEAM EPITAXY

ZnO layers have been grown on a-face sapphire substrates using H2O vapor and O2 plasma as O sources. The growth rate of H2O-vapor-assisted growth of ZnO (v-ZnO) is approx 3 times higher than that of plasma-assisted growth of ZnO (p-ZnO) for the same DEZn flux. This report addresses the higher growth activation of ZnO layers with H2O vapor than with O2 plasma at the same substrate temperature. A sharp and intense photoluminescence (PL) spectrum is observed in v-ZnO at the neutral donor-bound exciton energy of 3.368 eV at 16 K. The PL excitation spectrum measurement revealed A and B free exciton energies of 3.382 and 3.388 eV, resp. On the other hand, the p-ZnO showed the band-edge emission energy of 3.373 eV but with a weak PL intensity and broader half width. The PL intensity from v-ZnO was approx 104 times brighter than that of p-ZnO and the integrated PL intensity measured at RT was kept to approx 1/8 of that measured at 16 K. 14 refs.