Monolithic heterogeneous integration of Si photodetector and Van der Waals heterojunction with photocurrent enhancement

Abstract

Two-dimensional material has many novel features, which can be used to significantly improve the performance of traditional photonic and electronic devices. Therefore, the development of silicon/two-dimensional material monolithic heterogeneous integrated photodetector has attracted extensive attention worldwide. In this paper, we present a method to enhance the response of photocurrent of silicon-based PN junction photodetectors by using two-dimensional material Van der Waals heterostructures. The MoS2/graphene/N+ silicon monolithic heterogeneous integrated Van der Waals heterostructure is used as an NPN-type phototransistor to realize the amplification of photocurrent. When the device is irradiated, the photogenerated electron hole pairs in the semiconductor are separated by the applied electric field. However, graphene has a low density of defect states, and only a few electrons from N+ silicon can be recombined in graphene. Meanwhile, the graphene layer is very thin, and the positively biased graphene/N+ silicon junction and reversed-biased MoS2/graphene junction will accelerate the electrons to across the graphene layer and directly into MoS2. Using MXenes as the contact electrode of the MoS2 can eliminate the Fermi level pinning effect. The experimental results show that the photoresponsivity and photocurrent gain increase with the bias voltage, in the range of 0 to 5 V bias voltage. And the optical Ion/Ioff ratio increases by nearly 50 times. This research provides new insights for the detection of weak light and design for the photon computing device.