Shot noise measurements in a wide-channel transistor near pinch-off

TL;DR

This paper investigates shot noise in a high-frequency wide-channel transistor near pinch-off at 4.2K, revealing nonlinear noise behavior and enhanced Fano factor due to thermal fluctuations, not increased partition noise.

Contribution

It provides the first detailed analysis of shot noise behavior in a wide-channel transistor near pinch-off, highlighting thermal fluctuation effects.

Findings

Differential Fano factor exceeds 1/3 at low currents.

Noise spectral density shows slight nonlinearity with current.

Thermal fluctuations explain enhanced noise without invoking partition noise.

Abstract

We study a shot noise of a wide channel gated high-frequency transistor at temperature of 4.2K near pinch-off. In this regime, a transition from the metallic to the insulating state is expected to occur, accompanied by the increase of the partition noise. The dependence of the noise spectral density on current is found to be slightly nonlinear. At low currents, the differential Fano factor is enhanced compared to the universal value 1/3 for metallic diffusive conductors. We explain this result by the effect of thermal fluctuations in a nonlinear regime near pinch-off, without calling for the enhanced partition noise.