The Fe-Mg interplay and the effect of deposition mode in (Ga,Fe)N doped with Mg

TL;DR

This study investigates how Mg codoping and deposition mode affect Fe distribution and magnetic properties in (Ga,Fe)N layers grown by MOCVD, revealing that codoping and deposition mode influence Fe incorporation, aggregation, and magnetic behavior.

Contribution

It demonstrates the impact of Mg codoping and deposition mode on Fe distribution, magnetic properties, and nanocrystal formation in (Ga,Fe)N layers, combining experimental and theoretical insights.

Findings

Homogeneous Mg doping reduces Fe incorporation efficiency.

Homogeneous Mg doping changes magnetization from ferromagnetic to paramagnetic.

Digital deposition promotes Fe aggregation and nanocrystal formation.

Abstract

The effect of Mg codoping and its deposition mode on the Fe distribution in (Ga,Fe)N layers grown by metalorganic vapor phase epitaxy is investigated. Both homogeneously- and digitally-Mg codoped samples are considered and contrasted to the case of (Ga,Fe)N layers obtained without any codoping by shallow impurities. The structural analysis of the layers by high-resolution transmission electron microscopy and by high-resolution- and synchrotron x-ray diffraction gives evidence of the fact that in the case of homogenous-Mg doping, Mg and Fe competitively occupy the Ga-substitutional cation sites, reducing the efficiency of Fe incorporation. Accordingly, the character of the magnetization is modified from ferromagnetic-like in the non-codoped films to paramagnetic in the case of homogeneous Mg codoping. The findings are discussed vis-`a-vis theoretical results obtained by ab initio computations, showing only a weak effect of codoping on the pairing energy of two Fe cations in bulk GaN. However, according to these computations, codoping reverses the sign of the paring energy of Fe cations at the Ga-rich surface, substantiating the view that the Fe aggregation occurs at the growth surface. In contrast to the homogenous deposition mode, the digital one is found to remarkably promote the aggregation of the magnetic ions. The Fe-rich nanocrystals formed in this way are distributed non-uniformly, giving reason for the observed deviation from a standard superparamagnetic behavior.