The source of negative capacitance and anomalous peak in the forward bias capacitance-voltage in Cr/p-si Schottky barrier diodes (SBDs)

The frequency and voltage dependence of capacitance-voltage (C-V) and conductance-voltage (G/ω−V) characteristics of the Cr/p-Si metal semiconductor (MS) Schottky barrier diodes (SBDs) were investigated in the frequency and applied bias voltage ranges of 10 kHz to 5 MHz and (−4 V)−(+4 V), respectively, at room temperature. The effects of series resistance (Rs) and density distribution of interface states (Nss), both on C-V and G/ω−V characteristics were examined in detail. It was found that capacitance and conductance, both, are strong functions of frequency and applied bias voltage. In addition, both a strong negative capacitance (NC) and an anomalous peak behavior were observed in the forward bias C-V plots for each frequency. Contrary to the behavior of capacitance, conductance increased with the increasing applied bias voltage and there happened a rapid increase in conductance in the accumulation region for each frequency. The extra-large NC in SBD is a result of the existence of Rs, Nss and interfacial layer (native or deposited). In addition, to explain the NC behavior in the forward bias region, we drew the C-I and G/ω−I plots for various frequencies at the same bias voltage. The values of C decrease with increasing frequency at forward bias voltages and this decrease in the NC corresponds to an increase in conductance. The values of Nss were obtained using a Hill-Coleman method for each frequency and it exhibited a peak behavior at about 30 kHz. The voltage dependent profile of Rs was also obtained using a Nicollian and Brews methods.