Giant Negative Photoconductivity in a Van Der Waals Heterojunction‐Based FET with Bidirectional Photoresponse

ABSTRACT Phototransistors with the bidirectional photoresponse (positive and negative photoconductivity, PPC and NPC) have broad prospects for novel and multifunctional applications. Herein, a novel strategy is proposed to achieve bidirectional photoresponse in a vertical /UVO‐InSe field‐effect transistor (FET) with ultraviolet‐ozone (UVO) oxidized InSe nanosheets. It exhibits a giant NPC performance with a high I / I ratio (6.32 × 10 5 ), responsivity ( = −1.56 × 10 5 A W −1 ) and remarkable operational stability. In a further step, the separation‐transport‐recombination process of photogenerated carriers has been investigated under various gate voltages for the physical mechanism of bidirectional photoconductivity. Particularly, the accumulation and recombination of electrons and holes at the /UVO‐InSe interface could induce the giant NPC effect. Moreover, information protection and pattern recognition systems are realized based on the PPC and NPC effects. This study highlights the promising potential of the van der Waals heterojunction‐based FETs with bidirectional photoresponse for multifunctional optoelectronic devices.