Ultrahigh photoresponsivity MoS₂ photodetector with tunable photocurrent generation mechanism

Photodetectors with two-dimensional (2D) materials on a SiO₂/Si substrate have been extensively explored. However, these photodetectors often suffer from a large gate voltage and relatively low photoresponsivity due to the low efficiency light absorption of 2D materials. Here, we develop a MoS₂ photodetector based on the Al₂O₃/ITO (indium tin oxide)/SiO₂/Si substrate with ultrahigh photoresponsivity of 2.7 ×10⁴ A W^-1. Most of the incident light is reflected by the interface of stacked Al₂O₃/ITO/SiO₂ substrate, which significantly increases the light absorption of 2D materials. With the help of thinner and high-κ Al₂O₃ dielectric, the current ON/OFF ratio could exceed 10⁹ with a gate voltage no more than 2 V. Enhanced gate regulation also brings about a relatively high mobility of 84 cm² V^-1 s^-1 and subthreshold swing of 104 mV dec^-1. Additionally, two different photocurrent generation mechanisms have also been revealed by tuning the gate voltage. The reflection-enhancement substrate assisted MoS₂ photodetector provides a new idea for improving the performance of 2D material photodetectors, which can be perfectly combined with other methods.