Photoresponse Properties of Ambipolar Transport in WSe2 Field-Effect Transistors

Abstract

This study investigates the photoresponse properties of two-dimensional (2D) tungsten diselenide (WSe2) ambipolar field-effect transistors (FETs), distinguishing three distinct transport regions based on major charge carrier types: unipolar, saturation, and ambipolar transport. The ambipolar transport characteristics of WSe2 FETs change under light illumination. Specifically, the critical drain voltage, at which a sharp increase in drain current occurs, shifts under illumination toward the positive gate voltage direction due to the photogating effect. Unlike traditional avalanche photodetectors, which suffer from material degradation due to high-energy collisions of charge carriers such as electrons and holes, the photodetector with ambipolar transport enhances device stability and longevity by operating at lower electric fields. Experimental results demonstrate that the ambipolar WSe2 FETs can achieve a specific detectivity of 3 × 108 Jones in the ambipolar transport region, which is 104 Jones order higher than that in the unipolar region. This study highlights the potential for enhanced performance of ambipolar 2D devices in optoelectronic applications.