Investigating electrical properties of highly resistive ZnO films using a parallel dipole line hall effect system

Electrical properties of as-deposited, annealed, and CdCh treated ZnO films were investigated using an ultra-sensitive PDL Hall effect system. Carrier concentration, mobility, and conductivity of the films were extracted from Hall effect measurements. Previous thinner ZnO films deposited by RF sputtering were insulating, and no linear 1-V response or useful signal from the Hall effect measurements could be obtained. In this study, some of the thicker ZnO films deposited at different substrate temperatures have shown an improved 1- V response with an enhanced Hall signal. This has enabled reliable carrier concentration and mobility values to be extracted. 750 nm thick as-deposited ZnO films at substrate temperature of 500∘C resulted in an average carrier concentration of 4.24×10¹³cm⁻³ . A further increase in carrier concentration has been observed when films were annealed at 500°C under vacuum, and CdCl₂ treated.