Gate-Driven Bi-Directional Photoresponse in MoTe₂ Based Field Effect Transistors

A flexible, multi-mode and adaptable response plays a crucial role in the design of next generation devices to keep up with the rise of neuro-artificial intelligence. A bidirectional behavior, which consists in the coexistence of positive and negative photoconductivity (PPC and NPC), is required as a first ingredient to enable multi-dimensional information expansion. In this context, transistors based on ambipolar twodimensional (2D) materials offer great opportunities for next generation nanophotonic devices. In this study we investigate the gate-driven bidirectionality of a MoTe2-based field effect transistor in high vacuum. The device shows an ambipolar transfer characteristic that evolves from a p- to an n-type dominant behavior, and we monitored the main figures of merit over time. It exhibits a tunable photoresponse under the illumination of a white supercontinuum laser that strongly depends on the operating conditions. We demonstrate that both PPC and NPC can be induced by changing the applied gate voltage. The hysteretic behavior of MoTe₂ enables further information channels, since the photocurrent sign and intensity also depend on the previous history of the material. In the end, we explore the switching properties of the device to sequences of laser pulses of increasing intensity.