Depth profiling of optical and vibrational properties in GaN/AlN quantum dot superlattices

Abstract

AbstractSpatially resolved confocal μ‐Raman and μ‐photoluminescence experiments were performed to analyze the vibrational and optical properties of GaN/AlN quantum dots as a function of depth. Two approaches have been followed. First, spectra were taken by defocusing the microscope objective at various depths on the sample surface. In a second set of experiments a bevel at an angle of 20° with respect to the surface normal was prepared by mechanical polishing of the surface, and spectra were taken across the bevel. The E2h vibrational modes ascribed to the GaN QDs and the AlN spacer redshift towards the surface, indicating the progressive relaxation of the QDs and a considerable increase of the tensile strain in the AlN spacer. The photoluminescence is found to blueshift and narrow towards the surface. This behaviour is ascribed to the decrease of the QD internal electric field as a consequence of the relaxation. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)