MoS2 bipolar junction photo-transistor (BJPT) with high gain and millisecond speed

Semiconducting two-dimensional (2D) MoS2 has emerged as a promising material for logic transistors and photodetectors, benefiting from its considerable mobility and strong light–mater interaction, along with the low cost and large area growth. However, the reported MoS2 based photodiode and photoconductor suffer from either absence of gain or slow dynamic response, limiting their practical application with high sensitivity. Herein, the lateral bipolar junction photo-transistors (BJPT) with both PNP and NPN architectures are fabricated by partial chemical doping, which combine the advantages of both photodiode and photoconductor by producing a high photo-gain of ∼103 electrons per photon adsorption due to the carrier amplification and remaining a well dynamic response with speed less than 10 ms. In this device, we achieve a high responsivity of 2 × 103 A/W and high sensitivity with specific D* up to 7.2 × 1011 Jones at 635 nm in the amplification region. This work demonstrates a BJPT device scheme that can combine both high gain and fast temporal response in a single device, promoting the wide applications of 2D ultra-thin photodetectors.