Modification of GaN thin film on sapphire substrate optical properties under weak magnetic fields

Abstract

We present a study of the modifications to the optical transmittance of GaN thin film on sapphire due to weak magnetic field (WMF) treatment. Measurements were performed in the 320–1100 nm wavelength range at 300 K, evidencing a change in transmission spectra for wavelengths above 700–800 nm after the WMF treatment. We use a model with three layers to simulate transmittance spectra. We have found that changes of the optical thickness induced by WMF are not sufficient to explain discrepancies between experimental and simulated spectra. To obtain a complete agreement it is necessary to consider a change in the refractive index of GaN and/or in the reflection coefficients for the interface air-GaN. We interpret such WMF-related effects as due to the diffusion of point defects after dissolution of metastable complexes from inner boundaries to surface of the structure. These defects modify optical properties of the GaN film.