Dual-gate MoS2phototransistor with atomic-layer-deposited HfO2as top-gate dielectric for ultrahigh photoresponsivity.

An asymmetric dual-gate (DG) MoS2field-effect transistor (FET) with ultrahigh electrical performance and optical responsivity using atomic-layer-deposited HfO2as a top-gate (TG) dielectric was fabricated and investigated. The effective DG modulation of the MoS2FET exhibited an outstanding electrical performance with a high on/off current ratio of 6 × 108. Furthermore, a large threshold voltage modulation could be obtained from -20.5 to -39.3 V as a function of the TG voltage in a DG MoS2phototransistor. Meanwhile, the optical properties were systematically explored under a series of gate biases and illuminated optical power under 550 nm laser illumination. An ultrahigh photoresponsivity of 2.04 × 105AW-1has been demonstrated with the structure of a DG MoS2phototransistor because the electric field formed by the DG can separate photogenerated electrons and holes efficiently. Thus, the DG design for 2D materials with ultrahigh photoresponsivity provides a promising opportunity for the application of optoelectronic devices.