Negative Photoconductance in van der Waals Heterostructures-Based Floating Gate Phototransistor

TL;DR

This paper reports the first observation of negative photoconductance in van der Waals heterostructure-based floating gate phototransistors, demonstrating gate-tunable transitions and potential for light-tunable multi-bit memory applications.

Contribution

It is the first to demonstrate negative photoconductance in vdW heterostructures and explores its control for advanced memory device functionalities.

Findings

Observation of negative photoconductance in ReS2/h-BN/MoS2 heterostructures.

Gate-tunable transition between positive and negative photoconductance.

Potential for light-tunable multi-bit memory devices.

Abstract

Van der Waals (vdW) heterostructures made of two-dimensional materials have been demonstrated to be versatile architectures for optoelectronic applications due to strong light-matter interactions. However, most of light-controlled phenomena and applications in the vdW heterostructures rely on positive photoconductance (PPC). Negative photoconductance (NPC) has not yet been reported in vdW heterostructures. Here we report the observation of the NPC in ReS2/h-BN/MoS2 vdW heterostructures-based floating gate phototransistor. The fabricated devices exhibit excellent performance of nonvolatile memory without light illumination. More interestingly, we observe a gate-tunable transition between the PPC and the NPC under the light illumination. The observed NPC phenomenon can be attributed to the charge transfer between floating gate and conduction channel. Furthermore, we show that the control of NPC through light intensity is promising in realization of light-tunable multi-bit memory devices. Our results may enable potential applications in multifunctional memories and optoelectronic devices.