Ultrahigh photoresponsivity MoS 2 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 Al2 O3 /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 Al2 O3 /ITO/SiO2 substrate, which significantly increases the light absorption of 2D materials. With the help of thinner and high-κ Al2 O3 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.