Scaling Analysis of High Gain Monolayer MoS2 Photodetector for Its Performance Optimization

Monolayer MoS
₂
photodetectors are modeled and simulated by self-consistently solving diffusive transport equations in the presence of light illumination and carrier recombination with the 2-D Poisson equation. The simulated results indicate that very high photoresponsivity (PR) of ~1000 A/W observed in others' experiments is due to strong electrostatic effect of pile up of optically generated holes, and efficient optical absorption. It is found that the value of PR is sensitive to gate bias voltage, and the photodetector performance can be improved by decreasing hole mobility if side effects of low hole mobility, such as high recombination rate, slow response speed, and more noise, are suppressed. High quality monolayer MoS
₂
with large electron mobility and less Shockley-Read-Hall recombination defects is desired for achieving high performance. The PR increases as the gate insulator thickness increases. The channel length needs to be carefully designed by considering the carrier recombination behavior in monolayer MoS
₂
. The optimization method of monolayer MoS
₂
photodetectors proposed here is also applicable to other monolayer transition-metal dichalcogenide materials in general.