Unipolar transport and shot noise in metal-semiconductor-metal structures

TL;DR

This paper develops a comprehensive analytical model for unipolar current and noise in metal-semiconductor-metal structures, revealing complex noise behavior and a transition from thermal to shot noise across different injection regimes.

Contribution

It introduces a self-consistent analytical theory that accounts for diffusion current effects, covering the entire range from low to high injection levels in these structures.

Findings

Structures exhibit shot noise at high voltages.

Crossover from Nyquist to shot noise shows a complex dependence, including a double thermal noise regime.

Noise behavior transitions from square root to cubic power law with increasing current.

Abstract

We carry out a self-consistent analytical theory of unipolar current and noise properties of metal-semiconductor-metal structures made of highly resistive semiconductors in the presence of an applied bias of arbitrary strength. By including the effects of the diffusion current we succeed to study the whole range of carrier injection conditions going from low level injection, where the structure behaves as a linear resistor, to high level injection, where the structure behaves as a space charge limited diode. We show that these structures display shot noise at the highest voltages. Remarkably the crossover from Nyquist noise to shot noise exhibits a complicate behavior with increasing current where an initial square root dependence (double thermal noise) is followed by a cubic power law.