Enhancement in structural, elemental and optical properties of boron–phosphorus Co-doped ZnO thin films by high-temperature annealing

Abstract

The inherent n-type nature of zinc oxide (ZnO) and its unstable p-type behavior with single dopant species have encouraged researchers to explore the effect of multiple dopants as a viable solution for long-term stability and repeatability. Herein, we report boron (B) and phosphorus (P) co-doped ZnO thin films engineered through an optimized ion implantation technique followed by annealing at 1000 °C in oxygen ambiance. We investigated their structural, chemical, and optical properties to capture the effect of both boron implantation duration and annealing temperature. Co-doping with boron was observed to boost phosphorus incorporation in the film. Compared with P-doping, P–B co-doping increased the dominance of acceptor-bound exciton peak and also, suppressed non-radiative/visible emission which is due to reduced Madelung energy. After high-temperature annealing at 1000 °C, further narrowing of optical emission peaks generated due to acceptor incorporation was observed. Also, the co-doped samples showed stability in the acceptor behavior for more than one year.