On the Frequency and Voltage-Dependent Profiles of the Surface States and Series Resistance of Au/ZnO/n-Si Structures in a Wide Range of Frequency and Voltage

In order to interpret the electrical characteristics of fabricated Au/ZnO/n-Si structures as a function of frequency and voltage well, their capacitance–voltage ( C – V ) and conductance–voltage ( G / ω – V ) measurements were carried out in a wide range of frequencies (0.7 kHz–2 MHz) and voltages (± 6 V) by 50 mV steps at room temperature. Both the C – V and G / ω – V plots have reverse, depletion, and accumulation regions such as a metal–insulator/oxide semiconductor (MIS or MOS) structures. The values of doped-donor atoms ( N D ), Fermi energy level ( E F ), barrier height (Φ B ), and series resistance ( R s ) of the structure were obtained as a function of frequency and voltage. While the value of N D decreases with increasing frequency almost as exponentially, the value of depletion width ( W D ) increases. The values of C and G / ω increase with decreasing frequency because the surface states ( N ss ) are able to follow the alternating current (AC) signal, resulting in excess capacitance ( C ex ) and conductance ( G ex / ω ), which depends on their relaxation time and the frequency of the AC signal. The voltage-dependent profiles of N ss were obtained from both the high–low frequency capacitance and Hill-Colleman methods. The other important parameter R s of the structure was also obtained from the Nicollian and Brews methods as a function of voltage.