Self-interaction effects in (Ga,Mn)As and (Ga,Mn)N

TL;DR

This study compares electronic structures of Mn-doped GaAs and GaN using LSDA and a new pseudo-SIC method, revealing different self-interaction effects and implications for ferromagnetism mechanisms.

Contribution

It introduces a pseudo-SIC approach to better account for strong correlation effects in Mn-doped semiconductors, clarifying their electronic and magnetic properties.

Findings

LSDA accurately models (Ga,Mn)As with weak self-interaction effects.

LSDA incorrectly predicts (Ga,Mn)N band structure due to strong self-interaction.

Pseudo-SIC reveals localized Mn 3d bands and confined holes in (Ga,Mn)N.

Abstract

The electronic structures of Mn-doped zincblende GaAs and wurtzite GaN are calculated using both standard local-density functional theory (LSDA), and a novel pseudopotential self-interaction-corrected approach (pseudo-SIC), able to account for the effects of strong correlation. We find that, as expected, the self-interaction is not strong in (Ga,Mn)As, because the Fermi energy is crossed by weakly correlated As p - Mn d hybridized bands and the Mn 3d character is distributed through the whole valence band manifold. This result validates the extensive literature of LSDA studies on (Ga,Mn)As, including the conclusion that the ferromagnetism is hole-mediated. In contrast, the LSDA gives a qualitatively incorrect band structure for (Ga,Mn)N, which is characterized by localized Mn 3d bands with very strong self-interaction. Our pseudo-SIC calculations show a highly confined hole just above the Fermi energy in the majority band manifold. Such a band arrangement is consistent with (although by no means conclusive evidence for) a recent suggestion that formation of Zhang-Rice magnetic polarons is responsible for hole-mediated ferromagnetism in (Ga,Mn)N.