Tunable Linearity of High-Performance Vertical Dual-Gate vdW Phototransistors

Layered 2D semiconductors have been widely exploited in photodetectors due to their excellent electronic and optoelectronic properties. To improve their performance, photogating, photoconductive, photovoltaic, photothermoelectric, and other effects have been used in phototransistors and photodiodes made with 2D semiconductors or hybrid structures. However, it is difficult to achieve the desired high responsivity and linear photoresponse simultaneously in a monopolar conduction channel or a p–n junction. Here, dual-channel conduction with ambipolar multilayer WSe₂ is presented by employing the device concept of dual-gate phototransistor, where p-type and n-type channels are produced in the same semiconductor using opposite dual-gating. It is possible to tune the photoconductive gain using a vertical electric field, so that the gain is constant with respect to the light intensity—a linear photoresponse, with a high responsivity of ≈2.5 × 10⁴ A W⁻¹. Additionally, the 1/f noise of the device is kept at a low level under the opposite dual-gating due to the reduction of current and carrier fluctuation, resulting in a high detectivity of ≈2 × 10¹³ Jones in the linear photoresponse regime. The linear photoresponse and high performance of the dual-gate WSe₂ phototransistor offer the possibility of achieving high-resolution and quantitative light detection with layered 2D semiconductors.