Impurity Band Conduction in a High Temperature Ferromagnetic Semiconductor

TL;DR

This study uses optical spectroscopy to demonstrate that in Ga$_{1-x}$Mn$_{x}$As, the Fermi energy is located within a Mn-induced impurity band, providing insights into its conduction mechanism and transport properties.

Contribution

It provides direct evidence that the Fermi level in Ga$_{1-x}$Mn$_{x}$As lies in an impurity band, advancing understanding of its electronic structure and conduction behavior.

Findings

Fermi energy resides in a Mn-induced impurity band

Carriers have a large effective mass supporting impurity band conduction

Insights into transport properties of Mn-doped GaAs

Abstract

The band structure of a prototypical dilute ferromagnetic semiconductor, Ga$_{1-x}$Mn$_{x}$As, is studied across the phase diagram via optical spectroscopy. We prove that the Fermi energy ($E_{F}$) resides in a Mn induced impurity band (IB). This conclusion is based upon careful analysis of the frequency and temperature dependence of the optical conductivity ($\sigma_{1}(\omega,T)$). From our analysis of $\sigma_{1}(\omega,T)$ we infer a large effective mass ($m^*$) of the carriers, supporting the view that conduction occurs in an IB. Our results also provide useful insights into the transport properties of Mn-doped GaAs.