Hole sp3-character and delocalization in (Ga,Mn)As revised with pSIC and MLWF approaches - newly found spin-unpolarized gap states of s-type below 1% of Mn

TL;DR

This study revises the electronic structure of dilute (Ga,Mn)As using advanced DFT methods, revealing new spin-unpolarized gap states at low Mn doping levels that impact its magnetic and conductive properties.

Contribution

It introduces the use of pSIC and MLWF approaches to accurately characterize hole states and uncovers previously unknown s-type impurity states below 1% Mn doping.

Findings

70% of HDF is within inter-impurity regions at low doping

3-5% contribution of Mn 3d states at 1-3% doping

Discovery of spin-unpolarized s-type impurity states below 1% doping

Abstract

The dilute magnetic semiconductor (Ga,Mn)As is ferromagnetic in accordance with the p-d Zener model. Hole density function (HDF) localization has been previously studied by means of the density functional theory (DFT) and non-standard DFT methods; however not for dopings near 1%. We have revised (Ga,Mn)As using the DFT with the pseudopotential self-interaction correction (pSIC) and maximally-localized Wannier functions (MLWFs), which show the sp3 character of a HDF. Nature of HDF is extended - for low dopings and the pSIC, 70% of the HDF is located within the inter-impurities region, and contribution of the 3d-Mn states is 3-5% for 1-3% of Mn with the pSIC, and 11% with the DFT. We found that for dopings below 1%, the spin-unpolarized s-type impurity states segregate from the conduction band to the energy gap - in contrast to earlier publications. This implies that donor co-doped dilute samples would be both insulating and nonmagnetic.