Enhanced photoresponsivity of multilayer MoS2 transistors using high work function MoOx overlayer

Abstract

Using thin sub-stoichiometric molybdenum trioxide (MoOx, x < 3) overlayer, we demonstrate over 20-folds enhanced photoresponsivity of multilayer MoS2 field-effect transistor. The fabricated device exhibits field-effect mobility (μFE) of up to 41.4 cm2/V s and threshold voltage (VTH) of −9.3 V, which is also modulated by the MoOx overlayer. The MoOx layer (∼25 nm), commonly known for a high work function (∼6.8 eV) material with a band gap of ∼3 eV, is evaporated on top of the MoS2 channel and confirmed by the transmission electron microscope analysis. The electrical and optical modulation effects are associated with interfacial charge transfer and thus an induced built-in electric field at the MoS2/MoOx interface. The results show that high work function MoOx can be a promising heterostructure material in order to enhance the photoresponse characteristics of MoS2-based devices.