Abstract
Two different approaches of contactless modulated reflectivity spectroscopy, namely photoreflectance (PR) and contactless electroreflectance (CER), have been used for the investigation of quasi 0D self‐assembled semiconductor structures, like quantum dots or quantum dashes. First of all, the advantages and disadvantages of both techniques are discussed with respect to that certain application, including the problems of spurious background signals and below‐band‐gap oscillations. Second, the modulation mechanism in photoreflectance of quantum dots is analyzed by comparing PR, CER, photoluminescence excitaion and photoreflectance excitation. Finally, recent results regarding the modulation spectroscopy study of several types of structures including quasi 0D objects will be presented. It will concern the following aspects in particular: wetting layer (WL) thickness determination; quantum dots formation at the 2D–3D Stranski–Krastanov growth transition for the case of In~x~ Ga~1–x~ As/GaAs quantum dots; probing the excited states and electronic structure in novel material/design QDot/QDash systems and characterization of the QD‐based laser structures. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)