Analysis of surface states and series resistance in Au/n-Si Schottky diodes with insulator layer using current-voltage and admittance-voltage characteristics

In order to good interpret the experimentally observed Au/n-Si (metal-semiconductor) Schottky diodes with thin insulator layer (18 Å) parameters such as the zero-bias barrier height (Φbo), ideality factor (n), series resistance (Rs) and surface states have been investigated using current-voltage (I-V), capacitance-frequency (C-f) and conductance-frequency (G-f) techniques. The forward and reverse bias I-V characteristics of Au/n-Si (MS) Schottky diode were measured at room temperature. In addition, C-f and G-f characteristics were measured in the frequency range of 1 kHz-1 MHz. The higher values of C and G at low frequencies were attributed to the insulator layer and surface states. Under intermediate forward bias, the semi-logarithmic Ln (I)-V plot shows a good linear region. From this region, the slope and the intercept of this plot on the current axis allow to determine the ideality factor (n), the zero-barrier height (Φbo) and the saturation current (IS) evaluated to 2.878, 0.652 and 3.61 × 10−7 A, respectively. The diode shows non-ideal I-V behavior with ideality factor greater than unity. This behavior can be attributed to the interfacial insulator layer, the surface states, series resistance and the formation barrier inhomogeneity at metal-semiconductor interface. From the C-f and G-f characteristics, the energy distribution of surface states (Nss) and their relaxation time (τ) have been determined in the energy range of (Ec − 0.493Ev)-(Ec − 0.610) eV taking into account the forward bias I-V data. The values of Nss and τ change from 9.35 × 1013 eV−1 cm−2 to 2.73 × 1013 eV−1 cm−2 and 1.75 × 10−5 s to 4.50 × 10−4 s, respectively.