Gate-Tunable Electronic Structure of Black Phosphorus/HfS2 P–N van der Waals Heterostructure with Uniformly Anisotropic Band Dispersion

Black phosphorus (BP)-based heterostructure with tunable band offset has been proven to be promising for rectifier diode and photoelectronic devices. However, it is usually not easy to find a suitable material to construct the heterojunction because the necessary type-II band structure and the strong unintentional p-type doping of BP should be both considered. Therefore, most of studies mainly focused on certain 2D materials, like MoS2 and WSe2. However, the low mobility of these materials greatly hinders the further promotion of device performance. For the first time, we demonstrate that HfS2, which has been proven to possess a much higher mobility of electrons and has been experimentally synthesized recently, fully satisfies conditions of heterostructure with BP. The heterojunction could be used as a tunable optoelectronic device and rectifier diode. With external normal electric field, the efficiency of photon-generated charge separation and rectification ratio could be manipulated. In addition, what is interesting is that the nanostructure presents an unexpected highly anisotropic band dispersion along orthogonal directions, which suggests a superior transport performance with both high mobility and carrier density.