How Do Quantum Effects Influence the Capacitance and Carrier Density of Monolayer MoS 2 Transistors?

When transistor gate insulators have nanometer-scale equivalent oxide thickness (EOT), the gate capacitance ( C G ) becomes smaller than the oxide capacitance ( C ox ) due to the quantum capacitance and charge centroid capacitance of the channel. Here, we study the capacitance of monolayer MoS 2 as a prototypical two-dimensional (2D) channel while considering spatial variations in the potential, charge density, and density of states. At 0.5 nm EOT, the monolayer MoS 2 capacitance is smaller than its quantum capacitance, limiting the single-gated C G of an n -type channel to between 63% and 78% of C ox , for gate overdrive voltages between 0.5 and 1 V. Despite these limitations, for dual-gated devices, the on-state C G of monolayer MoS 2 is 50% greater than that of silicon at 0.5 nm EOT and more than three times that of InGaAs at 1 nm EOT, indicating that such 2D semiconductors are promising for improved gate control of nanoscale transistors at future technology nodes.