Noise and charge discreteness as ultimate limit for the THz operation of ultra-small electronic devices

TL;DR

This paper models the fundamental noise limits in ultra-small electronic devices operating at Terahertz frequencies, revealing that quantum charge discreteness imposes an ultimate size and frequency constraint.

Contribution

It introduces a quantum measurement-based model for THz noise in nano-electronic devices, linking noise to device size and operational frequency.

Findings

Intrinsic THz noise increases as device volume decreases.

Ultra-small devices cannot operate effectively at THz frequencies due to fundamental noise limits.

Scaling down device size conflicts with achieving high-frequency operation.

Abstract

To manufacture faster electron devices, the industry has entered into the nanoscale dimensions and Terahertz (THz) working frequencies. The discrete nature of the few electrons present simultaneously in the active region of ultra-small devices generate unavoidable fluctuations of the current at THz frequencies. The consequences of this noise remain unnoticed in the scientific community because its accurate understanding requires dealing with consecutive multi-time quantum measurements. Here, a modeling of the quantum measurement of the current at THz frequencies is introduced in terms of quantum (Bohmian) trajectories. With this new understanding, we develop an analytic model for THz noise as a function of the electron transit time and the sampling integration time, which finally determine the maximum device working frequency. The model is confirmed by either semi-classical or full-quantum time-dependent Monte Carlo simulations. All these results show that intrinsic THz noise increases unlimitedly when the volume of the active region decreases. All attempts to minimize the low signal-to-noise ratio of these ultra-small devices to get effective THz working frequencies are incompatible with the basic elements of the scaling strategy. One can develop THz electron devices, but they cannot have ultra-small dimensions. Or, one can fabricate ultra-small electron devices, but they cannot be used for THz working frequencies.