High-Quality Reconfigurable Black Phosphorus p-n Junctions

The p-n junction is the fundamental building block for electronics and photonics applications. In a conventional p-n junction, the performance parameters cannot be tuned due to the fixed doping level after ion implantation. In this paper, reconfigurable p-n or n-p junctions were built based on the ambipolar black phosphorus (BP) and other 2-D materials, namely, graphene and hexagonal boron nitride (h-BN). High-quality graphene/h-BN/BP/h-BN sandwich device was created by the dry transfer method in an inert environment. Graphene serves as the local back gate, which can tune BP partially into either n-type or p-type material. The rest of the BP channel can be controlled by the back gate. The BP encapsulated device can enable the high performance of the ideality factor down to 1.08 (p-n junction) and 1.18 (n-p junction). The device developed in this paper has a more balanced ideality factor than previously reported reconfigurable WSe2 and BP devices. By tuning the back gate and graphene gate, the BP device can be tuned into four operational quadrants, namely, n-n, n-p, p-n, and pp junctions. Moreover, the hole mobility of BP is up to 404 cm
²
/V · s at room temperature. Our work shows that the BP heterostructure is very promising for high-speed reconfigurable logic functions and circuits.