Papers by Keyword: SiGe/Si Heterostructures

Abstract: First relaxation stages in Si1-x Gex layers on Si substrates are induced by annealing of metastable, low-temperature buffer layer samples and observed by X-ray topography (XRT). This method allows observing large area (several square millimetres) of a sample and reveals very low densities of defects, located in the layer as well as in the substrate. It allow to follow the evolution of the very first steps of the relaxation, starting with dislocation crosses which were characterized and evolving to misfit dislocation network by very low increases of thermal budget. It is proposed a nucleation mechanism of these crosses based on Frank loops due to point defects condensation which can transform locally in glide dislocations under the influence of the biaxial stress in the film.

Abstract: We present experimental data on the effect of low-temperature buffer layers on the dislocation structure formation in SiGe/Si strained-layer heterostructures under thermal annealing. Specific subjects include mechanisms of misfit dislocation nucleation, propagation and multiplication as well as the role of intrinsic point defects in these processes. Samples with lowtemperature Si (400°C) and SiGe (250°C) buffer layers were grown by MBE. In general, the processes of MD generation occur similarly in the heterostructures studied independently of the alloy composition (Ge content: 0.15, 0.30) and kind of buffer layer. Intrinsic point defects related to the low-temperature epitaxial growth influence mainly the rate of misfit dislocation nucleation.