Highly efficient tunable photodetector with a bipolar response in van der Waals heterojunctions

The heterojunction integration of two-dimensional (2D) materials via van der Waals (vdW) forces, unencumbered by lattice and processing constraints, constitutes an efficacious approach to enhance the overall optoelectronic performance of photodetectors, due to an assortment of distinctive light-matter interactions. Nonetheless, vdW heterojunction photodetectors based on transition metal dichalcogenides (TMDs) face an inevitable trade-off between low dark currents and high responsivity, curtailing the application potential of myriad novel optoelectronic components in sensing, spectral, and communication systems. In this study, we present the successful actualization of a highly sensitive, self-powered, and gate-tunable bipolar response photodetector. The mechanisms underlying photocurrent generation were scrutinized via bias-, power-, and position-dependent mapping photo-response measurements, identifying the photovoltaic effect, which is attributable to the Schottky junction's built-in electric field, as the predominant mechanism. The prototype Au-WS2-graphene photodetector exhibits a remarkable light on/off ratio of 1.2 x 10(6), a specific detectivity of 6.12 x 10(11) cm Hz(1/2) W-1 with 20 mu s response time at 638 nm. The wide gate-tunable responsivity provides an adjustability scope, ranging from 0.9 to 3.1 A W-1. Notably, the device demonstrates an exceptional linear photo-current response, with a linear dynamic range (LDR) value approximating 130 dB, which significantly surpasses that of other photodetectors based on TMDs.