Arsenic doping for synthesis of nanocrystalline p-type ZnO thin films

Nanocrystalline p-type arsenic-doped ZnO (ZnO:As) films have been synthesized on (0001) sapphire substrates by pulsed laser deposition using a ZnO target mixed with 6.6wt% As2O3. The process of synthesizing p-type ZnO:As films was performed in an ambient gas of ultrapure (<99.99%) oxygen. The ambient gas pressure was 5Pa with the substrate temperature in the range of 350–500°C. The ZnO:As films grown at 500°C are p type, and the acceptor concentration in ZnO:As films is about 1.9×1018at.∕cm3 as determined by Hall effect measurements. The concentration of As in ZnO:As films is estimated to be about 1.7% from the x-ray photoemission spectroscopy (XPS) spectrum. Guided by the XPS analysis and a model for large-sized-mismatched group-V dopant in ZnO, an AsZn–2VZn complex was thought to be the most possible acceptor.