Effect of (O, As) dual implantation on p-type doping of ZnO films

Optical and electrical characteristics of ZnO films co-implanted with O and As ions have been investigated by photoluminescence (PL), Hall-effect, and current-voltage (I-V) measurements. 100-nm-thick ZnO films grown on n-type Si (100) wafers by RF sputtering have been implanted with various fluences of 30 keV O and 100 keV As ions at room temperature, and subsequently annealed at 800°C for 20 min in a N₂ ambient. The dually-implanted ZnO films show stable p-type characteristics for particular implant combinations, consistent with the observation of dominant PL peaks at 3.328 and 3.357 eV that are associated with the acceptor levels. For these dually-implanted p-type ZnO films/n-type Si diodes, the I-V curves show rectifying p-n junction behavior. Other singly (As)- or dually-implanted samples show n-type or indeterminable doping characteristics. These results suggest that O implantation plays a key role in forming p-type ZnO films by reducing the oxygen vacancy concentration and facilitating the formation of As-related acceptors in ZnO.