title: Mechanisms of photoconductivity in atomically thin MoS2.
abstract: Atomically thin transition metal dichalcogenides have emerged as promising candidates for sensitive photodetection. Here, we report a photoconductivity study of biased mono- and bilayer molybdenum disulfide field-effect transistors. We identify photovoltaic and photoconductive effects, which both show strong photogain. The photovoltaic effect is described as a shift in transistor threshold voltage due to charge transfer from the channel to nearby molecules, including SiO2 surface-bound water. The photoconductive effect is attributed to the trapping of carriers in band tail states in the molybdenum disulfide itself. A simple model is presented that reproduces our experimental observations, such as the dependence on incident optical power and gate voltage. Our findings offer design and engineering strategies for atomically thin molybdenum disulfide photodetectors, and we anticipate that the results are generalizable to other transition metal dichalcogenides as well.
authors.affiliation: Vienna University of Technology, Institute of Photonics , Gußhausstraße 27-29, 1040 Vienna, Austria.
authors.forename: Marco M
authors.initials: MM
authors.lastname: Furchi
authors.forename: Dmitry K
authors.initials: DK
authors.lastname: Polyushkin
authors.forename: Andreas
authors.initials: A
authors.lastname: Pospischil
authors.forename: Thomas
authors.initials: T
authors.lastname: Mueller
keywords: Transition-metal dichalcogenides; molybdenum disulfide; photoconductive effect; photovoltaic effect