Parameters affecting the electrical and optical properties of p-type aluminum-doped ZnO: A review

This paper reviews the effects of the operating parameters on the optical and electrical properties of p-type aluminum-doped ZnO (AZO) films. In addition, the most well-known fabrication routes used in the preparation of p-type AZO, such as magnetron sputtering, sol–gel, ultra spray pyrolysis, are introduced. This paper focuses on the effects of the annealing temperature, gas ambient and dopant concentration, which have significantly effects on the electrical and optical properties of p-type AZO. The findings showed that the dopant types and concentrations, and annealing conditions have significant effects on the optical and electrical properties of p-type AZO. Furthermore, the paper discusses the mechanism of p-type conversion as well as new types of transition metal-doped AZO, which can achieve p-type conductivity with low resistivity. Overall, this paper provides an overview of p-type AZO films and the prospects of developing highly conducting p-type composite transparent conducting oxides for optoelectronic devices.