Defect–defect magnetic coupling in Gd doped GaN epitaxial films: A polarization selective magneto-photoluminescence study

Abstract

Here, we have carried out a magnetic field dependent polarization selective photoluminescence (PL) study at 1.5 K on Gd-doped GaN epitaxial layers grown on c-SiC substrates, where the incorporation of Gd has been found to generate three types of defects, which results in bound excitonic features in low temperature PL spectra. The study reveals that the external magnetic field dependence of the spin-flip scattering rates for the three excitonic features shows an increasing tendency of saturation at high fields as the density of these defects increases in these layers. This suggests that the signals must be stemming from defects which are ferromagnetically coupled with each other. This is further confirmed by the study carried out on a GaN sample co-doped with Si and Gd, where defects are found to be ferromagnetically coupled, while the Si-donors do not.