Optical conductivity of Mn doped GaAs

TL;DR

This paper models the optical conductivity of Mn-doped GaAs, successfully matching experimental data and revealing its proximity to the metal-insulator transition with implications for doping strategies.

Contribution

It provides a non-perturbative theoretical analysis of optical conductivity in GaMnAs, accurately reproducing experimental observations and elucidating the phase diagram near the metal-insulator transition.

Findings

Compensation causes a red shift in the optical peak.

GaMnAs is close to the metal-insulator transition.

Optical effective mass is approximately twice the electron mass.

Abstract

We study the optical conductivity in the III-V diluted magnetic semiconductor GaMnAs and compare our calculations to available experimental data. Our model study is able to reproduce both qualitatively and quantitatively the observed measurements. We show that compensation (low carrier density) leads, in agreement to the observed measurements to a red shift of the broad peak located at approximately 200 meV for the optimally annealed sample. The non perturbative treatment appears to be essential, otherwise a blueshift and an incorrect amplitude would be obtained. By calculating the Drude weight (order parameter) we establish the metal-insulator phase diagram. We indeed find that Mn doped GaAs is close to the metal-insulator transition and that for 5$%$ and 7$%$ doped samples, 20$%$ of the carriers only are delocalized. We have found that the optical mass is approximately 2 m$_{e}$. We have also interesting results for overdoped samples which could be experimentally realized by Zn codoping.