Enhancing Photoresponsivity of Self-Aligned MoS₂ Field-Effect Transistors by Piezo-Phototronic Effect from GaN Nanowires

We report high-performance self-aligned MoS₂ field-effect transistors (FETs) with enhanced photoresponsivity by the piezo-phototronic effect. The FETs are fabricated based on monolayer MoS₂ with a piezoelectric GaN nanowire (NW) as the local gate, and a self-aligned process is employed to define the source/drain electrodes. The fabrication method allows the preservation of the intrinsic property of MoS₂ and suppresses the scattering center density in the MoS₂/GaN interface, which results in high electrical and photoelectric performances. MoS₂ FETs with channel lengths of ∼200 nm have been fabricated with a small subthreshold slope of 64 mV/dec. The photoresponsivity is 443.3 A·W^-1, with a fast response and recovery time of ∼5 ms under 550 nm light illumination. When strain is introduced into the GaN NW, the photoresponsivity is further enhanced to 734.5 A·W^-1 and maintains consistent response and recovery time, which is comparable with that of the mechanical exfoliation of MoS₂ transistors. The approach presented here opens an avenue to high-performance top-gated piezo-enhanced MoS₂ photodetectors.