P-type arsenide doping of zinc oxide: thermal evolution of defects

Abstract

Zinc oxide is a direct wide band gap material having excellent optical properties. It has attracted extnesive attention because of ite potential in ultra violet optoelectronic device applications. The asymmetric p-type doping difficulty has hindered the realization of practical ZnO-based devices for many years. As-doped ZnO films exhibits thermally induced conductivity type change from highly resistive n-type to p-type having hole concentration of ~10^{18} cm^{-3}. Further thermal treatment will then convert the p-type conductivity to highly resistive n-type again. Compreheasive spectroscopic characterization including X-ray spectroscopy, positron annihilation spectroscopy, photoluminescence, secondary ion mass spectroscopy, and transmission electron microscopy shows that the p-type conductivity conversion is associated with the formation of the shallow acceptor As_{Zn}-2V_{Zn} defect complex. The loss of the p-type conductivity is related to the thermal dissociation of the shallow acceptor complex and the formation of isolated Zn-vacancy at the ZnO-film/substrate interface.