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

Abstract

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.

Keywords: HfO2; MoS2; dual-gate; photoresponsivity; phototransistor.