Electronic structure of (Ga,Mn)As revisited

TL;DR

This study uses angle resolved photoemission to reveal a highly dispersive Mn-induced energy band in (Ga,Mn)As, demonstrating that its electronic structure is a heavily modified host valence band with delocalized carriers responsible for ferromagnetism.

Contribution

First identification of a highly dispersive Mn-induced band in (Ga,Mn)As, clarifying the nature of carriers mediating ferromagnetism and resolving long-standing debate.

Findings

Mn induces a highly dispersive energy band in (Ga,Mn)As

Electronic structure is significantly modified from GaAs

Delocalized holes in the modified valence band enable ferromagnetic coupling

Abstract

The detailed nature of electronic states mediating ferromagnetic coupling in dilute magnetic semiconductors, specifically (Ga,Mn)As, has been an issue of long debate. Two confronting models have been discussed emphasizing host band vs. impurity band carriers. Using angle resolved photoemission we are for the first time able to identify a highly dispersive Mn-induced energy band in (Ga,Mn)As. Our results show that the electronic structure of the (Ga,Mn)As system is significantly modified from that of GaAs throughout the valence band. Close to the Fermi energy, the presence of Mn induces a strong mixing of the bulk bands of GaAs, which results in the appearance of a highly dispersive band in the gap region of GaAs. For Mn concentrations above 1% the band reaches the Fermi level, and can thus host the delocalized holes needed for ferromagnetic coupling. Overall, our data provide a firm evidence of delocalized carriers belonging to the modified host valence band.