Effects of s,p - d and s - p exchange interactions probed by exciton magnetospectroscopy in (Ga,Mn)N

TL;DR

This study uses magnetospectroscopy to analyze exchange interactions in (Ga,Mn)N, revealing non-standard exchange integrals and their effects on band gap and spin subband order, supported by recent theoretical models.

Contribution

It provides experimental evidence of exchange interactions in (Ga,Mn)N and explains unusual exchange integral signs through advanced theoretical frameworks.

Findings

Giant Zeeman splitting of excitons observed

Exchange integrals N0alpha and N0beta determined

Band gap increases with Mn concentration

Abstract

Near band-gap photoluminescence and reflectivity in magnetic field are employed to determine the exchange-induced splitting of free exciton states in paramagnetic wurtzite Ga1-xMnxN, x < 1%, grown on sapphire substrates by metal-organic vapor phase epitaxy. The band gap is found to increase with x. The giant Zeeman splitting of all three excitons A, B and C is resolved, enabling the determination of the apparent exchange integrals N0alpha(app) = 0.0 +/- 0.1 eV and N0beta(app) = +0.8 +/- 0.2 eV. These non-standard values and signs of the s - d and p - d exchange energies are explained in terms of recent theories that suggest a contribution of the electron-hole exchange to the spin splitting of the conduction band and a renormalization of the free hole spin-splitting by a large p - d hybridization. According to these models, in the limit of a strong p - d coupling, the band gap of (Ga,Mn)N increases with x and the order of hole spin subbands is reversed, as observed.