Improved detectivity and response speed of MoS phototransistors based on the negative-capacitance effect and defect engineering.

Due to the unique crystal structure, outstanding optoelectronic properties and a tunable band gap from 1.2-1.8 eV, two-dimensional molybdenum disulfide (MoS) has attracted extensive attention as a promising candidate for future photodetectors. In this work, a negative-capacitance (NC) MoS phototransistor is fabricated by using (HZO) as ferroelectric layer and AlO as matching layer, and a low subthreshold swing (SS) of 39 mV/dec and an ultrahigh detectivity of 3.736×10 cmHzW are achieved at room temperature due to the NC effect of the ferroelectric HZO. Moreover, after sulfur (S) treatment on MoS, the transistor obtained a lower SS of 33 mV/dec, a detectivity of 1.329×10 cmHzW and specially a faster response time of 3-4 ms at room temperature, attributed to the modulation of photogating effect induced by S-vacancy passivation in MoS by the S treatment. Therefore, the combination of the defect engineering on MoS and the NC effect from ferroelectric thin film could provide an effective solution for high-sensitivity phototransistors based on two-dimensional materials in the future.