Preparation of p-type ZnO film on the GaAs substrate by thermal annealing treatment

ZnO film with p-type conduction has been successfully prepared on the GaAs substrate grown by MOCVD process and by subsequent thermal annealing. The thermal annealing induces the diffusion of the As and Ga atoms from the GaAs substrate into the ZnO film to form acceptor defects for p-ZnO. From XPS spectra, the As atoms diffuse into the ZnO film after annealing at 600 °C and substitute the Zn site to form AsZn-2VZn, which is a complex acceptor defect to generate hole carriers for formation of p-type ZnO. The amount of Ga in the ZnO film is low compared with As after annealing. After annealing, the ZnO film is p-type with the hole carrier concentration of nearly 1019 cm− 3, and the hole mobility increases to 36 cm2/V s. From PL, the p-type ZnO has an obvious acceptor-bound exciton emission at 371 nm, confirming the formation of acceptor level. The stability of the p-type ZnO film preparation process is confirmed because the p-type conduction of ZnO film is reproducible. The annealing not only turns the conduction behavior of ZnO film into p-type but also improves the mobility of ZnO films.