# Impurity band conduction in group-IV ferromagnetic semiconductor Ge1-xFex with nanoscale fluctuations in Fe concentration

## TL;DR

This study investigates how impurity band conduction influences carrier transport and magnetic properties in Ge1-xFex ferromagnetic semiconductors with nanoscale Fe concentration fluctuations, revealing impurity band dominance at higher Fe levels.

## Contribution

It provides a detailed analysis of impurity band conduction mechanisms in Ge1-xFex films and how they relate to magnetic properties, including effects of boron doping.

## Key findings

- Transport is dominated by hole hopping in Fe-rich impurity bands at higher Fe concentrations.
- Boron doping does not significantly alter magnetic properties.
- Band profile models explain the observed transport and magnetic behaviors.

## Abstract

We study the carrier transport and magnetic properties of group-IV-based ferromagnetic semiconductor Ge1-xFex thin films (Fe concentration x = 2.3 - 14 %) with and without boron (B) doping, by measuring their transport characteristics; the temperature dependence of resistivity, hole concentration, mobility, and the relation between the anomalous Hall conductivity versus conductivity. At relatively low x (= 2.3 %), the transport in the undoped Ge1-xFex film is dominated by hole hopping between Fe-rich hopping sites in the Fe impurity band, whereas that in the B-doped Ge1-xFex film is dominated by the holes in the valence band in the degenerated Fe-poor regions. As x increases (x = 2.3 - 14 %), the transport in the both undoped and B-doped Ge1-xFex films is dominated by hole hopping between the Fe-rich hopping sites of the impurity band. The magnetic properties of the Ge1-xFex films are studied by various methods including magnetic circular dichroism, magnetization and anomalous Hall resistance, and are not influenced by B-doping. We show band profile models of both undoped and B-doped Ge1-xFex films, which can explain the transport and the magnetic properties of the Ge1-xFex films.

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Source: https://tomesphere.com/paper/1706.04445