Electrical transport and persistent photoconductivity in monolayer MoS₂ phototransistors

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 10⁴ 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 [Formula: see text] ON current as high as [Formula: see text] 10⁵ ON-OFF ratio, mobility of ∼1 cm² V^-1 s^-1 and photoresponsivity [Formula: see text].