Numerical Investigation of the Photogating Effect in MoTe2 Photodetectors

The necessity of overcoming the limitations (e.g. weight, cost and brittleness) of traditional bulk semiconductors employed to build conventional photodetectors, has fueled the interest of the scientific community towards two-dimensional crystals. Its most representative member, graphene [1], with outstanding electrical and mechanical properties, has however a severely limited photoresponsivity due to 1) the lack of bandgap and 2) a reduced carrier lifetime that hardly reaches a few picoseconds [2]. Greater expectations lay on Transition Metal Dichalcogenides (TMDs) [3], the bandgap of which is sensitive to the number of layers. Moreover, TMDs can be stacked forming vertical or lateral heterojunctions [4] giving rise to structures similar to field-effect transistors (FETs) that behave as photodetectors. In this work we theoretically study the optoelectronic properties of a backgated phototransistor, with its channel formed by few-layer MoTe2, and we focus on the role played by the charges trapped at the channel-insulator interface through the photogating effect [5, 6].