Electrical transport and persistent photoconductivity in monolayer MoS2 phototransistors

TL;DR

This study investigates the electrical transport and persistent photoconductivity in monolayer MoS2 transistors, revealing effects like photogating, space charge limited conduction, and long-lasting photoconductivity due to charge trapping.

Contribution

It provides detailed analysis of photoconductive effects and persistent photoconductivity mechanisms in monolayer MoS2 transistors under various illumination conditions.

Findings

Photoconductivity increases logarithmically with light intensity.

Persistent photoconductivity lasts over 10^4 seconds due to charge trapping.

Devices show high ON-OFF ratio and photoresponsivity of 1 A/W.

Abstract

We study electrical transport properties in exfoliated molybdenum disulfide (MoS2) back-gated field effect transistors at low drain bias and under different illumination intensities. It is found that photoconductive and photogating effect as well as space charge limited conduction can simultaneously occur. We point out that the photoconductivity increases logarithmically with the light intensity and can persist with a decay time longer than 10^4 s, due to photo-charge trapping at the MoS2/SiO2 interface and in MoS2 defects. The transfer characteristics present hysteresis that is enhanced by illumination. At low drain bias, the devices feature low contact resistance of 1.4 k{\Omega}/{\mu}m, ON current as high as 1.25 nA/{\mu}m, 10^5 ON-OFF ratio, mobility of 1 cm^2/Vs and photoresponsivity R=1 A/W.