Monolayer MoS2 photodetectors with a buried-gate field-effect transistor structure.

Unlike zero-bandgap graphene, molybdenum disulfide (MoS2) has an adjustable bandgap and high light absorption rate, hence photodetectors based on MoS2 have attracted tremendous research attention. Most of the reported MoS2 photodetectors adopted back-gate field-effect transistor (FET) structure due to its easy fabrication and modulation features. However, the back-gate FET structure requires very high gate voltage up to 100 V, and it is impossible to modulate each device in an array with this structure independently. This work demonstrated a monolayer MoS2 photodetector based on a buried-gate FET structure whose experimental results showed that both the electrical and photoelectrical properties could be well modulated by a gate voltage as low as 3 V. A photoresponsivity above 1 A/W was obtained under a 395 nm LED light illumination, which is over 2 orders of magnitude higher than that of a reported back-gate photodetector based on monolayer MoS2 (7.5 mA/W). The photoresponsivity can be further improved by increasing the buried gate voltage and source-drain voltage. These results are of significance for the practical applications of MoS2 photodetectors, especially in the low voltage and energy-saving areas.