Effects of RF power variation on properties of ZnO thin films and electrical properties of p-n homojunction

A series of ZnO films with various radio-frequency (RF) powers were prepared on (0 0 1) GaAs substrate by RF magnetron sputtering. Scanning electron microscopy and X-ray rocking curve analyses were performed to investigate the effects of the RF power on the surface morphology and the crystallinity of the films. It was found that the RF power has affected the deposition rate, surface morphology, crystallinity, and optical properties of ZnO films. The films deposited at an RF power of 120W exhibited the best crystalline and optical properties with good surface morphology because of the balance between the number of the ZnO molecules arriving at the surface of the substrate and the surface diffusion of the ZnO molecules on the substrate. After post-annealing treatments at 600°C in vacuum, p-type ZnO films with the hall mobility in the range of 15-26 cm²/Vs were obtained because of As diffusion from substrate. To verify the p-type conductivity of ZnO films, the p-n homojunction of ZnO films was fabricated and the electrical properties were measured.