Valence-band structure of ferromagnetic semiconductor (InGaMn)As

TL;DR

This study uses resonant tunneling spectroscopy to investigate the valence-band structure of ferromagnetic (InGaMn)As, revealing that the valence band remains largely unchanged from the host semiconductor and that the Fermi level lies in the band gap.

Contribution

It provides systematic experimental evidence showing the valence band structure and negligible p-d exchange splitting in (InGaMn)As, challenging previous models of hole-mediated ferromagnetism.

Findings

Valence band remains similar to InGaAs.

Fermi level is in the band gap.

Negligible p-d exchange splitting.

Abstract

To clarify the whole picture of the valence-band structures of prototype ferromagnetic semiconductors (III,Mn)As (III: In and Ga), we perform systematic experiments of the resonant tunneling spectroscopy on [(In_0.53Ga_0.47)_1-x Mn_x]As (x=0.06-0.15) and In_0.87Mn_0.13As grown on AlAs/ In_0.53Ga_0.47As:Be/ p+InP(001). We show that the valence band of InGaMnAs almost remains unchanged from that of the host semiconductor InGaAs, that the Fermi level exists in the band gap, and that the p-d exchange splitting in the valence band is negligibly small in (InGaMn)As. In the In0.87Mn0.13As sample, although the resonant peaks are very weak due to the large strain induced by the lattice mismatch between InP and InMnAs, our results also indicate that the Fermi level exists in the band gap and that the p-d exchange splitting in the valence band is negligibly small. These results are quite similar to those of GaMnAs obtained by the same method, meaning that there are no holes in the valence band, and that the impurity-band holes dominate the transport and magnetism both in the InGaMnAs and In_0.87Mn_0.13As films. This band picture of (III,Mn)As is remarkably different from that of II-VI-based diluted magnetic semiconductors.