Fully Suspended MoS₂ Photodetectors toward High Response Speed and Stable Responsivity

High photoresponsivity has been achieved in photodetectors based on two-dimensional (2D) semiconductors, but they usually suffer from low response speed and severe responsivity decay with higher light intensity due to substrate effects. In this work, photodetectors with high response speed and stable responsivity are prepared based on fully suspended MoS2. Due to the complete separation of the suspended MoS2 channel and the Si substrate underneath, the photogating effect is effectively suppressed. Then the photocurrent rise and fall times are measured as 68.6 and 100.0 μs by transient photocurrent measurement, respectively, which are about 105 times faster than the nonsuspended devices. Moreover, they exhibit stable responsivity with time within a large range of light intensity. A detailed analysis of the photoresponse mechanisms is performed by comparing the photoresponses from devices with different structures. The results provide a fundamental understanding of photoresponse mechanisms and guide the design of high-performance 2D photodetectors.