Papers by Author: V.I. Vdovin

Abstract: Structural and luminescence properties have been studied in silicon layers with dislocation-related luminescence. Multiple room temperature implantation of oxygen ions with doses low than the amorphization threshold was carried out. Silicon ions with a dose exceeding the amorphization threshold by two orders of magnitude were implanted at a higher temperature (≥ 80°C). Both the implantations were not followed by the amorphization of the implanted layers. Annealing in a chlorine-containing atmosphere resulted in formation of extended structural defects and luminescence centers. Some regularities and peculiarities in the properties of the extended defects and dislocation-related luminescence lines were revealed in dependence on the implantation and annealing conditions.

Abstract: The nucleation of dislocation in semiconductors is still a matter of debate and especially in heteroepitaxial films. To understand this nucleation process the classical models of dislocation nucleation are presented and discussed. Two main points are then developed: emission of dislocations from surface steps and the role of point defects agglomeration on dislocation nucleation. Recent atomic simulation of half loops emission from surface steps and experimental evidences of anisotropic relaxation of GaInAs films deposited on vicinal (111) GaAs substrates strongly support surface steps as preferential sites for nucleation. In low temperature buffer layer structures (SiGe/Si) an original dislocation structure is observed which corresponds to the dislocation emission in different glide systems by a unique nucleation centre.

Abstract: Kinetics of oxide layer dissolution and atomic structure of Si-Si interface in Si wafer bonded structures have been investigated by transmission electron microscopy. Samples of Si(001)/SiO2/Si(001) and Si(110)/SiO2/Si(001) structures were fabricated by direct hydrophilic wafer bonding of 200 mm wafers followed by high temperature annealing. It is found that the decomposition rate of oxide layer and formation of Si-Si bonded interface depends very much on lattice mismatch and twist angle.

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: Structural defects in Si:Er layers grown by molecular beam epitaxy have been studied by transmission electron microscopy. Two kinds of second phase precipitates are the main defects in the layers with Er concentration ≥ 2х1019 cm-3: ball-shaped precipitates (4-25 nm) of metallic Er localized at the layer-substrate interface and platelet precipitates of ErSi2 extending through the whole layer. We studied the effect of Er concentration (8х1018 - 4х1019 cm-3) and growth temperature (400 - 700°C) on the defect generation. The peculiarities of defect generation in MBE Si:Er layers implanted with B+ ions were also studied.

Abstract: The samples of Cz Si were subjected to multi-step annealing at different temperatures. After high temperature consequent steps the dislocation related spectra (DRL) were detected from the samples. The main feature of the DRL spectra was the very narrow low energy bands D1/D2, which are unusual for Cz Si. TEM analysis shown that the only candidates for DRL spectra are dislocation loops, punched out from precipitates. To explain the absence of influence of oxygen it was assumed that the distribution of interstitial oxygen is nonuniform in such samples and has some depletion regions in the vicinity of precipitates.

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.