Gate controllable band alignment transition in 2D black-arsenic/WSe2 heterostructure

Controlling the manner of band alignment of heterostructures increases design freedom with novel physical properties, enables the design of new functional devices, and improves device performance, but the lattice matching limits the diversity of traditional heterostructures. Van der Waals heterostructures (vdWHs) fabricated by rationally mechanical restacking different two-dimensional (2D) layered materials or sequential synthesis can overcome this limitation. However, it is difficult to achieve full control over the band alignment for a specific vdWHs by means of an applied vertical electric field. Here, we take advantage of the band structure alignment properties of narrow-bandgap black-arsenic (b-As) and large-bandgap WSe2 to realize b-As/WSe2 vdWHs with type-I band alignment. The band alignment can be tuned from type I to type II by gate electric field, which greatly improves the photoresponsivity over 10(3). An ultra-fast photoresponse of about 570 ns is obtained, which is much better than that of vdWHs with the same structure. The b-As/WSe2 vdWHs also can achieve high-performance rectifier phototransistor with an ultra-high rectification ratio exceeding 10(6), a small conductance slope of about 86 mV/dec, and a low curvature coefficient of about 46 V-1. Our work paves the way for the exploitation of b-As heterojunction for ultra-fast and low-power optoelectronic applications.

Automated summary

Controlling the band alignment of heterostructures is important for designing novel physical properties and functional devices. Van der Waals heterostructures have the advantage of overcoming lattice matching limitations, but achieving full control over band alignment is challenging. In this study, black-arsenic (b-As)/WSe2 van der Waals heterostructures with type-I band alignment were realized and the band alignment could be tuned by a gate electric field, resulting in improved photoresponsivity and ultra-fast photoresponse.