Optical and electrical properties of ZnO doped with nitrogen using N2O plasma

초록

Nitrogen-doped ZnO thin films were grown by sputtering[1]. Nitrogen was doped using N2O plasma during sputtering process[2]. Carrier concentrations and mobilities of the films were determined by Hall effect measurement. Photoluminscence (PL) spectroscopy and X-ray diffraction (XRD) analyses were performed to investigate the optical properties and the crystallinity of the films, respectively. High temperature annealing markedly improves the quality of the ZnO crystal grown on the single crystal sapphire substrate by magnetron sputtering (Fig.1) The electron concentration and the mobility in the ZnO films doped more heavily with nitrogen using N2O plasma decrease more rapidly with the increase of the annealing temperature (Fig. 2 and 3). This implies that growth of a ZnO thin film with a higher nitrogen doping concentration followed by higher temperature annealing could change n-type ZnO to p-type eventually by higher compensation of the intrinsic n type defects such as oxygen vacancies and zinc interstitials. The electrical property of the ZnO thin film tends to change from n-type to p-type as the N2O/Ar gas flow ratio increases. Also it was found that the PL intensity of the ZnO film increased but the crystallinity decreased as the N2O/Ar gas flow ratio increased.