Behavior of phonons in short period GaN‐AlN superlattices

Abstract

This work deals with short period GaN-AlN superlattices, studied by Raman spectroscopy using visible and ultraviolet excitations. The E2 (high) and E1(TO) phonons show a two-mode behavior. In contrast, we observed an unique spectral line in the A1(TO) spectrum: its dependence on the mean superlattice composition is in good agreement with recent theoretical results predicting its delocalized character. Two Raman lines strongly enhanced under ultraviolet excitations, were observed in the A1(LO) spectrum. Lattice dynamical simulations within the Rigid Ion Model have been performed to assign these Raman lines. The first one corresponds to an A1(LO) phonon confined in GaN wells. The second line is assigned to a dispersive B1 - like mode with an amplitude modulation similar to that of an interface mode. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)