There is Plenty of Room for THz Tunneling Electron Devices Beyond the Transit Time Limit

TL;DR

This paper introduces a new time-dependent model for tunneling electron devices operating above the transit time frequency limit, revealing intrinsic nonlinearities that could benefit THz applications and reduce device downscaling.

Contribution

A novel displacement current coefficient model valid for high frequencies, capturing nonlinear effects in tunneling devices beyond the transit time limit.

Findings

Displacement current dominates at frequencies above the transit time limit.

Tunneling devices exhibit intrinsic nonlinearities at THz frequencies.

Nonlinearities can be advantageous for THz applications and device scaling.

Abstract

The traditional transmission coefficient present in the original Landauer formulation, which is valid for quasi-static scenarios with working frequencies below the inverse of the electron transit time, is substituted by a novel time-dependent displacement current coefficient valid for frequencies above this limit. Our model captures in a simple way the displacement current component of the total current, which at frequencies larger than the inverse of the electron transit time can be more relevant than the particle component. The proposed model is applied to compute the response of a resonant tunneling diode from 10$\,$GHz up to 5$\,$THz. We show that tunneling electron devices are intrinsically nonlinear at such high frequencies, even under small-signal conditions, due to memory effects related to the displacement current. We show that these intrinsic nonlinearities (anharmonicities) represent an advantage, rather than a drawback, as they open the path for tunneling devices in many THz applications, and avoid further device downscaling.