Wavelength-Controlled Photocurrent Polarity Switching in BP-MoS2 Heterostructure

Abstract

Layered 2D van der Waals semiconductors and their heterostructures have been shown to exhibit positive photoconductance (PPC) in many studies. A few recent reports have demonstrated negative photoconductance (NPC) as well that can enable broadband photodetection besides multi-level optoelectronic logic and memory. Controllable and reversible switching between PPC and NPC is a key requirement for these applications. This report demonstrates visible-to-near infrared wavelength-driven NPC and PPC, along with reversible switching between the two, in an air stable, high mobility, broadband black phosphorus field effect transistor covered with a few layer MoS₂ flake. The crossover switching wavelength can be tuned by varying the MoS₂ bandgap through its flake thickness and the NPC and PPC photoresponsivities can be modulated using electrostatic gating as well as laser power. Recombination-driven NPC and PPC, as supported by density functional theory calculations, allows for reversible switching. Further, gate voltage-dependent negative persistent photoconductance is well-suited for optosynaptic applications.