Electrical and optical properties of P-doped ZnO thin films by annealing temperatures in Nitrogen ambient

The effects of post-annealing temperature on the optical and electrical properties of P-doped ZnO thin films, grown on sapphire substrate, have been investigated when the annealing is performed under nitrogen ambient. Analysis of the XRD shows that regardless of the post-annealing temperature, the P-doped ZnO thin films have grown the (002) peak. The full width of half maximum decreases from 0.194 to 0.181° as the annealing temperature increases from 700 to 900 °C. This phenomenon means that the increase of annealing temperature causes enhancement of the thin film’s crystalline properties. The results of Hall effect measurements indicate that the P-doped ZnO thin films, annealed at 750 and 800 °C exhibit p-type behavior, with hole concentrations of 5.71 × 1017 cm−3 and 1.20 × 1018 cm−3, and hole mobilities of 0.12 cm2/Vs and 0.08 cm2/Vs, respectively. The low-temperature (10 K) photoluminescence results reveal that the peaks related to the neutral-acceptor exciton (A0X) at 3.355 eV, free electrons to neutral acceptor (FA) at 3.305 eV and donor acceptor pair (DAP) at 3.260 and 3.170 eV are observed in the films showing p-type behavior with the acceptors. Because P atoms replace O atoms to produce acceptors from P-doped ZnO thin films by the thermal activation process at the appropriate annealing temperature with nitrogen ambient, the p-type ZnO thin films can be fabricated in this way.