Raman resonance in the strained Ge quantum dot array

We study the Raman resonance of a Ge quantum dot (QD) array grown pseudomorphically to a Si matrix using low-temperature molecular-beam epitaxy. A change of the resonance energy and the shape of the resonance curve in comparison with bulk Ge are observed. These features are shown to be explained by taking into account QD strain and the quasistationary character of the electronic states responsible for the observed resonance. Application of a model of the two-dimensional critical point of the interband density of states allows us to estimate the damping parameter and localization size of these states. It is shown that the observed enhancement of the resonance amplitude in a QD array as compared to the bulk case is related to transformation of the interband density of states into the δ-function due to quantization of the electron-hole spectrum