Study on the electrical properties of ZnSe/Si heterojunction diode
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ZnSe thin film is e-beam evaporated on monocrystalline p-Si to fabricate n-ZnSe/p-Si heterojunction. The electrical properties were investigated by current-voltage (I-V), capacitance-voltage (C-V) and conductance-voltage (G/w-V) measurements. The forward bias I-V characteristics were analyzed in the temperature range of 220-360 K. The fabricated diode structure exhibited rectifying characteristics with a two order rectification ratio. The current transport in the junction was modeled by the modification of thermionic emission (TE) in which the observed anomaly was related to the interfacial disorder at the junction. From this analysis, the zero-bias barrier height and ideality factor at room temperature condition were determined as 0.775 and 3.195 eV, respectively. The TE anomaly was also evaluated by considering the fluctuations due to the barrier inhomogeneity and the assumption of Gaussian distribution in barrier height. Therefore, the forward bias I-V results were used to determine the density of interface states. The frequency dependence of C-V and G/w-V characteristics of the n-ZnSe/p-Si heterostructure were studied by taking into account of the effect of the series resistance and interface states at room temperature. According to the high-low frequency capacitance and Hill-Coleman methods, density of interface states was calculated and these experimental values were found in decreasing behavior with increasing frequency. The voltage and frequency dependence of series resistance values obtained from C-V and G/w-V measurements were also related to the insulator layer and the distribution density of interface states.