Raman Scattering in GaN/AlN Quantum Dot Structures

Abstract

The strain field in the surrounding AlN matrix of GaN quantum dot layers, vertically stacked along the [0001] growth direction, is studied through its effects on the AlN E2 phonon frequency. Comparison is made between a structure composed of large, vertically correlated quantum dots and a less densely stacked system of smaller, uncorrelated dots. We find evidence for a mean extensive strain state of the AlN matrix in the former structure associated with local strain favoring the vertical alignment of the dots. Scattering by the A1(LO) phonon of the uncorrelated smaller dots is observed under resonant conditions when using a laser excitation approaching the fundamental transition energy of the quantum dots.