Magnetoresistance in semiconductor structures with hopping conductivity: effects of random potential and generalization for the case of acceptor states

TL;DR

This paper revisits the theory of magnetoresistance in hopping semiconductors, highlighting the impact of random potential on tunneling and extending models to acceptor states, aligning with experimental findings.

Contribution

It introduces a revised model accounting for background impurity potential effects and generalizes magnetoresistance mechanisms to acceptor states in 2D structures.

Findings

Random potential shortens tunneling range, reducing negative magnetoresistance.

Extended models show acceptor states can dominate magnetoresistance at low temperatures.

Results align semi-quantitatively with experimental data.

Abstract

We reconsider the theory of magnetoresistance in hopping semiconductors. First, we have shown that the random potential of the background impurities affects significantly preexponential factor of the tunneling amplitude which becomes to be a short-range one in contrast to the long-range one for purely Coulomb hopping centers. This factor to some extent suppresses the negative interference magnetoresistance and can lead to its decrease with temperature decrease which is in agreement with earlier experimental observations. We have also extended the theoretical models of positive spin magnetoresistance, in particular, related to a presence of doubly occupied states (corresponding to the upper Hubbard band) to the case of acceptor states in 2D structures. We have shown that this mechanism can dominate over classical wave-shrinkage magnetoresistance at low temperatures. Our results are in semi-quantitative agreement with experimental data.