Optical Phonon Limited High Field Transport in Layered Materials

TL;DR

This paper models high-field electron transport in layered 2D materials considering optical phonon interactions, providing benchmarks and insights into their suitability for high-frequency and high-power electronic applications.

Contribution

It introduces an optical phonon limited velocity model for layered 2D materials and evaluates their high-field transport limits, highlighting the potential of h-BN for high-power devices.

Findings

Transition metal dichalcogenides have modest optical phonon limited velocities compared to silicon.

h-BN shows promise for high-frequency high-power devices due to large optical phonon energy.

Experimental saturation velocities in MoS2 align with model predictions.

Abstract

An optical phonon limited velocity model has been employed to investigate high-field transport in a selection of layered 2D materials for both, low-power logic switches with scaled supply voltages, and high-power, high-frequency transistors. Drain currents, effective electron velocities and intrinsic cut-off frequencies as a function of carrier density have been predicted thus providing a benchmark for the optical phonon limited high-field performance limits of these materials. The optical phonon limited carrier velocities of a selection of transition metal dichalcogenides and black phosphorus are found to be modest as compared to their n-channel silicon counterparts, questioning the utility of these devices in the source-injection dominated regime. h-BN, at the other end of the spectrum, is shown to be a very promising material for high-frequency high-power devices, subject to experimental realization of high carrier densities, primarily due to its large optical phonon energy. Experimentally extracted saturation velocities from few-layer MoS2 devices show reasonable qualitative and quantitative agreement with predicted values. Temperature dependence of measured vsat is discussed and found to fit a velocity saturation model with a single material dependent fit parameter.