Phonon localization in cubic GaN/AlN superlattices

Abstract

To enhance the device’s performance a better understanding of the confinement of polar optical-phonons in the heterostructures should be achieved. In this work, we investigated a set of three cubic GaN/AlN superlattices (SL) grown by plasma-assisted Molecular Beam Epitaxy (MBE) on 3C–SiC substrates by structural and optical measurements. Reciprocal Space Mapping (RSM) at the (113) reflections revealed the SL satellite peaks and the strain in the structures as well photoluminescence spectra evidence the quantum confinement. Different line broadenings in the Raman spectra measured in each heterostructure indicate that the longitudinal optical phonons of GaN describe different localization lengths. Through the application of the spatial correlation model we have quantified the localization length of these phonons and established a correlation with the GaN layer thicknesses. For the first time it is presented localized optical phonons (LO) in cubic GaN layers.