An Alternative Approach to Voltage Dependent Reduction of Schottky Barrier Height Modeling in Two Dimensional MSM Photodetectors

Current-voltage (I-V) characteristics of a two dimensional MSM photodetector can be explained by modified thermionic emission diffusion (TED) theory. The theory assumes that Schottky barrier height (SBH) decreases linearly with bias voltage and hence voltage dependent reduction of SBH is under-stood in term of a series resistance ( Rs) and ideality factor (n). Characterization of Rs and n can be done from [dV/d(lnI)] vs I plot. However, in this paper we are presenting an alternative approach to understanding characteristics of voltage dependent reduction of SBH. We are proposing an exponential relationship between reduction of SBH and bias voltage to understand non ideality of Schottky junctions. By applying this relationship directly into the Richardson-Dushman equation photocurrents of different Transition-Metal Dichalcogenides(TMD) based devices can be estimated analytically. This model offers a simplistic approach for understanding non ideal behaviour of Schottky barrier height. Using this model we have calculated I-V characteristics of four different TMD based photodetectors under illumination as reported in literature. We have observed good agreement of our calculated results with experimental values. Mean absolute error in each of the cases was found to be not more than 6% in these calculations.