Raman scattering in GaN/AlN quantum dot structures

The strain field in the surrounding AlN matrix of GaN quantum dot layers, v ertically stacked along the [0001] growth direction, is studied through its effects on the AlN E-2 phonon frequency. Comparison is made between a stru cture composed of large, vertically correlated quantum dots and a less dens ely stacked system of smaller, uncorrelated dots. We find evidence for a me an extensive strain state of the AlN matrix in the former structure associa ted with local strain favoring the vertical alignment of the dots. Scatteri ng by the A(1)(LO) phonon of the uncorrelated smaller dots is observed unde r resonant conditions when using a laser excitation approaching the fundame ntal transition energy of the quantum dots.