Analytical photoresponses of Schottky contact MoS2 phototransistors

TL;DR

This paper develops an analytical model for Schottky contact MoS2 phototransistors, revealing temperature-dependent contact behavior and providing insights into photoresponse mechanisms validated by experimental data.

Contribution

It introduces a new explicit analytical device model for Schottky contact MoS2 phototransistors that accounts for mixed thermionic emission and diffusion, improving understanding of their photoresponse.

Findings

Richardson constant of MoS2 Schottky contact is temperature dependent

Analytical photoresponse matches experimental data

Minority carrier recombination lifetimes are consistent with transient photoluminescence

Abstract

High-gain photodetectors based on two-dimensional (2D) semiconductors, in particular those in photoconductive mode, have been extensively investigated in the past decade. However, the classical photoconductive theory was derived on two misplaced assumptions. In this work, we established an explicit analytical device model for Schottky contact MoS2 phototransistors that fits well with experimental data. From the fitting results, we found that the Richardson constant of the MoS2 Schottky contact is temperature dependent, indicating that the Schottky contacts for the 2D material is best described by the mixed thermionic emission and diffusion model. Based on this device model, we further established an analytical photoresponse for the few-layer MoS2 phototransistors, from which we found the voltage distribution on the two Schottky contacts and the channel, and extracted the minority carrier recombination lifetimes. The lifetimes are comparable with the values found from transient photoluminescence measurements, which therefore validates our analytical photoresponses for Schottky contact 2D semiconducting phototransistors.