Raman scattering in InAs/AlGaAS quantum dot nanostructures

We report on Raman scattering experiments on InAs/Al(x)Ga(1-x)As quantum dot heterostructures with 0 < x <0.6. The samples were prepared by a technique that combines MBE and atomic layer MBE. For x > 0, we detected several lines originating from the Al(x)Ga(1-x)As alloy. These include scattering from GaAs-like and AlAs-like phonons with q near 0, and weaker scattering from disorder-activated phonons with q different from 0. In particular, we identified a line at ~ 250 cm-1 as due to disorder-activated longitudinal optical phonons in the alloy. This conclusion is different than the attribution of this line to scattering from dots and, consequently, we do not recognize the possibility of deriving any information about the actual composition of the dots from an analysis of this line as proposed by other authors.