Variation of the hopping exponent in disordered silicon MOSFETs

TL;DR

This study investigates how the hopping conduction mechanism in disordered silicon MOSFETs changes with disorder and electron density, indicating a possible transition from Mott to Anderson insulator states.

Contribution

It demonstrates the variation of the hopping exponent from 1/2 to 1/3 as a function of disorder and electron density in silicon MOSFETs, revealing a potential insulator transition.

Findings

Hopping exponent varies from 1/2 to 1/3 with disorder and density.

Magnetoconductivity supports a change in transport mechanism.

Evidence suggests a transition from Mott to Anderson insulator.

Abstract

We observe a complex change in the hopping exponent value from 1/2 to 1/3 as a function of disorder strength and electron density in a sodium-doped silicon MOSFET. The disorder was varied by applying a gate voltage and thermally drifting the ions to different positions in the oxide. The same gate was then used at low temperature to modify the carrier concentration. Magnetoconductivity measurements are compatible with a change in transport mechanisms when either the disorder or the electron density is modified suggesting a possible transition from a Mott insulator to an Anderson insulator in these systems.