Optimization of NC-LSPR coupled MoS2 phototransistors for high-performance broad-spectrum detection

Abstract

In this work, negative-capacitance (NC) and local surface plasmon resonance (LSPR) coupled MoS₂ phototransistors with a gate stack of HZO/AuNPs/Al₂O₃/MoS₂ are fabricated, and the impacts of Al₂O₃ interlayer-thickness (T_AlO) on the LSPR effect, the tensile strain on MoS₂ from the Au nanoparticles (AuNPs), the capacitance matching of the NC effect from Hf_0.5Zr_0.5O₂ (HZO) ferroelectric layer and the optoelectrical properties of the relevant devices are investigated. Through optimizing T_AlO, excellent optoelectrical properties of phototransistors with a T_AlO of 3 nm are achieved: a subthreshold swing (SS) of 25.76 mV/dec and ultrahigh detectivity of over 10¹⁴ Jones under 740 nm illumination. This is primarily because the NC-LSPR coupled structure can achieve an ultra-low SS through capacitance matching and a good interface passivation through optimizing Al₂O₃ interlayer to maintain effective LSPR and strain effects cross the MoS₂ to enhance optical absorption and detection range. This work provides a comprehensive analysis on effective distance range of the non-direct-contacted LSPR effect and its combination with capacitance matching of NC effect, culminating in an optimized NC-LSPR coupled MoS₂ phototransistor with a good consistency across an array of 30 devices, and offering a viable solution for the preparation of large-area, high-performance and broad-spectrum response 2D phototransistor array.