ReS₂/WSe₂ Type II Heterojunction Phototransitors with Integrated van der Waals Electrodes to Achieve Ultralow Dark Current and Fast Response Time

Recently, two-dimensional transition-metal dichalcogenides have become the focus of extensive research activities due to their remarkable physical properties such as high carrier mobility, tunable band gap, high optical response, and facile fabrication of heterostructures. In this study, we report on a type II van der Waals (vdW) heterojunction made of tungsten diselenide (WSe 2 ) and rhenium disulfide (ReS 2 ) with integrated vdW electrodes by using an all-dry transfer technique. The electrical rectified characteristics and photoelectrical response are analyzed in detail. Under 532 nm laser illumination, the ReS 2 /WSe 2 phototransistor exhibits a photovoltaic effect, showing a specific detectivity of 5.4 × 10 10 Jones and a fast impulse response time of 23.5/9 ms comparable to those of other devices with the similar structures. The junction is electrically tunable, and an atomically thin diode is realized under the appropriate gate bias. The atomically uniform and thin film without doping as well as integrated vdW electrodes not only simplifies the fabrication process but also enables the phototransistor to achieve ultralow dark current. The ReS 2 /WSe 2 heterojunction exhibits an ultralow off-state current of 32.5 pA and an excellent rectification ratio of 3.83 × 10 4 under modulation of the back-gate voltage. This study provides new guidelines for the design and preparation of high-performance ReS 2 /WSe 2 heterojunction optoelectronic devices.