Low residual doping level in homoepitaxially grown ZnO layers

Abstract

ZnO homoepitaxial growth is shown to change the luminescent properties of ZnO in a substantial way. Temperature dependent (4–300K) photoluminescence properties of the films grown by metal organic vapor phase epitaxy or by liquid phase epitaxy are compared to those of the hydrothermal ZnO substrate used for the growth. The intensity ratio between the free exciton and the donor bound exciton strongly increases, following homoepitaxial growth. The activation energy of the band edge emission intensity also increases from 13meV, which corresponds to the donor bound exciton localization energy, up to a value of 60meV, which corresponds to the free exciton binding energy. This indicates that homoepitaxial growth favors free exciton emission instead of donor bound exciton emission.