A Gaussian Thermionic Emission Model for Analysis of Au/MoS2 Schottky Barrier Devices

Abstract

Schottky barrier inhomogeneities are expected at the metal/TMDC interface and this can impact device performance. However, it is difficult to account for the distribution of interface inhomogeneity as most techniques average over the spot-area of the analytical tool, or the entire device measured for electrical I-V measurements. Commonly used models to extract Schottky barrier heights (SBH) neglect or fail to account for such inhomogeneities, which can lead to the extraction of incorrect SBH and Richardson constants. Here, we show that a gaussian modified thermionic emission model gives the best fit to experimental I-V-T data of van der Waals Au/p-MoS2 interfaces and allow the deconvolution of the SBH of the defective regions from the pristine region. By the inclusion of a gaussian distributed SBH in the macroscopic I-V-T analysis, we demonstrate that interface inhomogeneities due to defects are deconvoluted and well correlated to the impact on the device behavior across a wide temperature range from room temperature of 300 K down to 120 K. We verified the gaussian thermionic model across two different types of p-MoS2 (geological and synthetic), and finally compared the macroscopic SBH with the results of a nanoscopic technique, ballistic hole emission microscopy (BHEM). The results obtained using BHEM were consistent with the pristine Au/p-MoS2 SBH extracted from the gaussian modified thermionic emission model over hundreds of nanometers. Our findings show that the inclusion of Schottky barrier inhomogeneities in the analysis of I-V-T data is important to elucidate the impact of defects (e.g. grain boundaries, metallic impurities, etc.) and hence their influence on device behavior. We also find that the Richardson constant, a material specific constant typically treated as merely a fitting constant, is an important parameter to check for the validity of the transport model.