Probing the Optoelectronic Response of a Monolayer MoS$_{2}$ Field-Effect Transistor

Two-dimensional materials contain a wealth of interesting optoelectronic properties. Single-layer molybdenum disulfide (MoS$_{2})$, with its broken inversion symmetry, is of particular interest. This broken symmetry results in the formation of direct band gaps at the K and K' valleys in its band structure, allowing long-lived optical excitations. Furthermore, monolayer MoS$_{2}$ has valley-dependent electronic properties allowing confinement of charge carriers to a single valley by optical pumping [1]. We have fabricated two- and four-terminal devices based on single layers of MoS$_{2}$. We observe an efficient photocurrent response at the two-dimensional semiconductor-metal interface displaying Shottky diode behavior, in which an interfacial field splits excitons at the contacts to produce current. We also find that the photocurrent drastically increases under reverse biasing of the diode. Additionally we are exploring the dependence of this photocurrent response on the polarization state of incident light.\\[4pt] [1] Xiao, D., \textit{et al.}, \textit{Phys. Rev. Lett.} \textbf{108}, 196802 (2012).