Photovoltaic effects in reconfigurable heterostructured black phosphorus transistors

We demonstrate a reconfigurable black phosphorus electrical field transistor, which is van der Waals heterostructured with few-layer graphene and hexagonal boron nitride flakes. Varied homojunctions could be realized by controlling both source-drain and top-gate voltages. With the spatially resolved scanning photocurrent microscopy technique, photovoltaic photocurrents originated from the band-bending regions are observed, confirming nine different configurations for each set of fixed voltages. In addition, as a phototransistor, high responsivity (similar to 800 mA/W) and fast response speed (similar to 230 mu s) are obtained from the device. The reconfigurable van der Waals heterostructured transistors may offer a promising structure towards electrically tunable black phosphorus-based optoelectronic devices.