A semiquantitative approach to the impurity-band-related transport properties of GaMnAs nanolayers

TL;DR

This paper presents a semiquantitative model for understanding the impurity-band-related transport properties of GaMnAs nanolayers, linking magnetic order with resistivity behavior and explaining experimental resistivity humps.

Contribution

It introduces a self-averaged resistivity calculation that accounts for impurity band effects and magnetic order, providing new insights into transport mechanisms in GaMnAs nanolayers.

Findings

Metallic transport dominates at low temperature

Resistivity exhibits a hump near the transition temperature

Transport behavior depends on impurity band and magnetic order

Abstract

We investigate the spin-polarized transport of GaMnAs nanolayers in which a ferromagnetic order exists below a certain transition temperature. Our calculation for the self-averaged resistivity takes into account the existence of an impurity band determining the extended ("metallic" transport) or localized (hopping by thermal excitation) nature of the states at and near the Fermi level. Magnetic order and resistivity are inter-related due to the influence of the spin polarization of the impurity band and the effect of the Zeeman splitting on the mobility edge. We obtain, for a given range of Mn concentration and carrier density, a "metallic" behavior in which the transport by extended carriers dominates at low temperature, and is dominated by the thermally excited localized carriers near and above the transition temperature. This gives rise to a conspicuous hump of the resistivity which has been experimentally observed and brings light onto the relationship between transport and magnetic properties of this material.