Interface-Induced WSe In-plane Homojunction for High-Performance Photodetection.

2D transition metal dichalcogenides (TMDCs) have been extensively attractive for nano-electronics and nano-optoelectronics due to their unique properties. Especially, WSe, having bipolar carrier transport ability and sizable bandgap, is a promising candidate for future photodetectors. Here, we report an in-plane WSe homojunction formed by the interface gate of the substrate. In this architecture, an insulated h-BN flake was used to make only part of WSe flake contact substrate directly. Finally, the structures of WSe/substrate and WSe/h-BN/substrate construct an in-plane homojunction. Interestingly, the device can operate in both photovoltaic and photoconductive modes at different biases. As a result, a responsivity of 1.07 A W with a superior detectivity of over 10 jones and a fast response time of 106 μs are obtained simultaneously. Compared with previously reported methods adopted by chemical doping or electrostatic gating with extra bias voltages, our design provides a more facile and efficient way for the development of high-performance WSe-based photodetectors.