Ferromagnetic transition temperature enhancement in (Ga,Mn)As semiconductor by carbon co-doping

TL;DR

This paper theoretically investigates how carbon co-doping affects the ferromagnetic transition temperature in (Ga,Mn)As semiconductors, finding minimal electronic structure disruption but potential temperature enhancement.

Contribution

It introduces a combined phenomenological and microscopic model to analyze C co-doping effects on (Ga,Mn)As, demonstrating possible ferromagnetic temperature increases.

Findings

C has a small effect on electronic states near the valence band top.

The model of Mn-Mn coupling via itinerant holes remains valid with C doping.

C co-doping can enhance the ferromagnetic transition temperature.

Abstract

We present a theoretical study of (Ga,Mn)(As,C) diluted magnetic semiconductors with high C acceptor density that combines insights from phenomenological model and microscopic approaches. A tight-binding coherent potential approximation is used to describe the electronic structure in the presence of Mn$_{\rm Ga}$ and C$_{\rm As}$ impurities. We find only a small effect of C on the distribution and coherence of electronic states close to the top of the valence band and on the coupling between Mn moments, even at doping levels of several per cent. These results justify applying the model of ferromagnetic Mn-Mn coupling mediated by itinerant holes in the valence band also to C doped samples. The increase of ferromagnetic transition temperature due to the presence of C acceptors is illustrated by calculations that use the k.p Kohn-Luttinger description of the GaAs valence band and assume systems where Mn local moment and itinerant hole densities can be varied independently.