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

Matteo Villani,Werner Prost,Simone Clochiatti,Nils Weimann,Xavier Oriols

doi:10.1109/led.2021.3049229

Matteo Villani, Werner Prost + Show 3 more

Open Access

https://doi.org/10.1109/led.2021.3049229

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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.

Highlights

F OR high enough frequencies, it is said that electron devices behave as low pass filters
The usual strategy to design electron devices working at high frequencies is reducing their size to obtain smaller transit times
The model presented here, by construction valid beyond the transit time limit, shall spread the message of the title of this paper, opening intuition for quantum engineers to use the displacement current for new THz applications in electron tunneling devices

Summary

INTRODUCTION

F OR high enough frequencies, it is said that electron devices behave as low pass filters This behavior starts beyond the so-called transit time limit. Beyond the transit time limit, the displacement current component is known to become relevant over the particle one This contribution has been modeled previously using a master equation [8] or a scattering matrix [9], [10] to deal with electron transitions between different parts of the tunneling device. The model presented here, by construction valid beyond the transit time limit, shall spread the message of the title of this paper, opening intuition for quantum engineers to use the displacement current for new THz applications in electron tunneling devices

DISPLACEMENT CURRENT COEFFICIENT

SMALL-SIGNAL AND THZ NONLINEARITY IN TIME

SMALL-SIGNAL THZ NONLINEARITY IN FREQUENCY

CONCLUSION