Temperature-dependent electrical characterization of nitrogen-doped ZnO thin film: vacuum annealing effect

Abstract

Temperature-dependent Hall effect measurements were carried out at an N-doped ZnO thin film grown by the reactive sputtering method onto (001) Si substrate before and after being vacuum annealed at 900 °C. p-Type ZnO thin film was obtained with a relatively high mobility of ∼60 cm2 V−1 s−1, a high carrier concentration of 2.5×1017 cm−3 and a low resistivity of 0.4 Ω cm. After vacuum annealing, the temperature dependence of electrical parameters such as mobility and carrier concentration showed highly different characteristics. Time-resolved photoluminescence (TRPL), PL and x-ray diffraction measurements (XRD) were performed after the annealing process to check whether the high-temperature annealing can remove the ZnO film on Si or not. The PL measurement shows band-to-band recombination at 360 nm and TRPL shows the exciton recombination lifetime to be 571.7 ps. The XRD measurement reveals highly preferred c-axis (0002) orientation. Activation energies were calculated using the ln σ versus 1000 T−1 plot to be 20 meV for the as-grown and 24 and 6.8 meV after the vacuum annealing process.