Electronic structure of Ga$_{1-x}$Cr$_{x}$N and Si-doping effects studied by photoemission and X-ray absorption spectroscopy

TL;DR

This study investigates the electronic structure of Ga$_{1-x}$Cr$_{x}$N and the impact of Si doping using photoemission and X-ray absorption spectroscopy, revealing changes in oxidation states and electronic states near the Fermi level.

Contribution

It provides detailed spectroscopic analysis of Cr valence states and doping effects in GaN, highlighting the formation of Cr$^{2+}$ and potential cluster growth due to Si doping.

Findings

Cr in GaN is mainly trivalent, substituting Ga.

Si doping causes downward core level shifts and new states near Fermi level.

Si doping may induce Cr-rich cluster formation.

Abstract

The electronic structure of the magnetic semiconductor Ga$_{1-x}$Cr$_{x}$N and the effect of Si doping on it have been investigated by photoemission and soft x-ray absorption spectroscopy. We have confirmed that Cr in GaN is predominantly trivalent substituting for Ga, and that Cr 3$d$ states appear within the band gap of GaN just above the N 2$p$-derived valence-band maximum. As a result of Si doping, downward shifts of the core levels (except for Cr 2$p$) and the formation of new states near the Fermi level were observed, which we attribute to the upward chemical potential shift and the formation of a small amount of Cr$^{2+}$ species caused by the electron doping. Possibility of Cr-rich cluster growth by Si doping are discussed based on the spectroscopic and magnetization data.