On the frequency and voltage-dependent main electrical parameters of the Au/ZnO/n-GaAs structures at room temperature by using various methods

The surface states (Nss), relaxation time (τ), and series resistance (Rs) values as a function of frequency for various bias voltage of the metal-insulator-semiconductor (MIS) structure were obtained by using the impedance measurements which is including capacitance (C) and conductance (G/ω) in the frequency range of 0.5–500 kHz at room temperature. C/G-V plots for each frequency have inversion-depletion-accumulation regions and show a strong frequency and voltage-dependent at low-moderate frequencies due to the existence of Nss, Rs and Zinc Oxide (ZnO) interlayer. The parallel conductance (Gp/ω) between −2 and 1.5 V shows a distinctive peak for almost every voltage and its position shifts to higher frequencies with increasing voltage. The values barrier height (ФB), concentration of donor atoms (ND), and depletion layer thickness (WD) were calculated from the slope and intercept C−2-V plots as function of frequency. On the other hand, ideality factor (n), barrier-height (ΦBo) and Rs of the structure were calculated from both the thermionic-emission (TE) and Cheung functions which are usually good consisted with each other, some little discrepancies in them were attributed to the voltage-dependent of them and the nature of the used technique.