Systematic study of Mn-doping trends in optical properties of (Ga,Mn)As

TL;DR

This study systematically investigates how Mn doping affects the optical properties of (Ga,Mn)As epilayers, revealing trends that support a valence band model over an impurity band model for high doping levels.

Contribution

It provides a comprehensive analysis of optical property trends across various Mn doping levels, clarifying the electronic structure of highly doped (Ga,Mn)As.

Findings

Mid-infrared absorption peak blue-shifts with increased Mn doping

Magnetic circular dichroism peak shifts to higher energies as Mn doping increases

Results favor a valence band model over an impurity band model for high doping levels

Abstract

We report on a systematic study of optical properties of (Ga,Mn)As epilayers spanning the wide range of accessible substitutional Mn_Ga dopings. The growth and post-growth annealing procedures were optimized for each nominal Mn doping in order to obtain films which are as close as possible to uniform uncompensated (Ga,Mn)As mixed crystals. We observe a broad maximum in the mid-infrared absorption spectra whose position exhibits a prevailing blue-shift for increasing Mn-doping. In the visible range, a peak in the magnetic circular dichroism blue shifts with increasing Mn-doping. These observed trends confirm that disorder-broadened valence band states provide a better one-particle representation for the electronic structure of high-doped (Ga,Mn)As with metallic conduction than an energy spectrum assuming the Fermi level pinned in a narrow impurity band.