Papers by Author: Klara Lyutovich

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Authors: Klara Lyutovich, F. Ernst, Erich Kasper, Monika Bauer, Michael Oehme
Authors: Klara Lyutovich, Erich Kasper, Michael Oehme, Jens Werner, Tatiana S. Perova
Abstract: Molecular beam epitaxy is employed for the growth of strained-Si layers on top of virtual substrates with highly-relaxed ultrathin SiGe buffers in a continuous procedure. An initial growth stage at a temperature-ramp down to below 200°C causes misfit-dislocation generation by nucleation from point defects and provides an early relaxation in the SiGe buffers. In situ monitoring is used for the growth control. Layer thicknesses and composition are proved by ex situ spectroscopic ellipsometry. %Raman investigations on the layer stacks reveal high degrees of relaxation (70-100%) in sub-100nm SiGe buffer layers containing from 12 to 42 % Ge. Stress in strained Si layers estimated by means of Raman-spectra shift is adjustable from 0.92 to 6.84 GPa by the Ge-content in virtual substrates. Surface morphology of strained Si and of relaxed SiGe buffers is smooth and crosshatch-free. Device test structures show substantial increase of carrier mobilities in nMOSFETs fabricated on these strained-Si layers.
Authors: Erich Kasper, Klara Lyutovich
Abstract: Strain adjustment is obtained by virtual substrates which are composed of a silicon substrate and a strain relaxed buffer. The basics of strain relaxation are explained and applied to the covalent bonded Si/Ge system which shows a large regime of metastability. A solution to ultrathin strain relaxed buffers is given by the injection of point defects which nucleate to dislocation loops in the interface. Principle and injection mechanism are shown.
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