Papers by Author: Nikolai Yarykin

Abstract: The spectrum of defects produced by 5 MeV electron irradiation in oxygen-lean p-type silicon strongly contaminated with interstitial copper (Cu_i) is studied using the deep-level transient spectroscopy. It is observed that the room-temperature irradiation creates a large amount of Cu_PL centers (complexes including one substitutional and three interstitial Cu atoms). The analysis shows that this process is govern by formation of the substitutional copper atoms due to the direct reaction between irradiation-induced vacancies and mobile Cu_i species. This reaction consumes nearly all irradiation-induced vacancies and affects strongly the standard spectrum of radiation defects.

Abstract: The spectrum of defects produced by 5 MeV electron irradiation at room temperature in the oxygen-lean p-type silicon strongly contaminated with interstitial copper (Cu_i) is studied using the deep-level transient spectroscopy. It is observed that the interstitial carbon defects (C_i), which are abundant in irradiated copper-free samples, are not detected directly after irradiation. The phenomenon is attributed to the formation of a {Cu_i, C_i} complexes which exhibit no deep levels in the lower half of the band gap. The complexes are shown to dissociate under anneals at 300-340 K resulting in the appearance of the C_i species.

Abstract: Formation of the dislocation trails (DTs) left at the slip plane behind expanding dislocation half-loops is studied in Cz-Si plastically deformed at 600°C using the selective chemical etching and the EBIC and LBIC techniques which are sensitive to the defect recombination activity. It is found that the dislocation trails are qualitatively different for the half-loops expanded from the tensile and compressed surfaces of the bent sample. In the tensile part, DTs with the strongest recombination contrast are always revealed behind the 60oarm of the half-loops, while DTs are invisible (if exits at all) behind another arm and the bottom segment. The dissimilar behavior of two differently aligned 60° segments can be related to a different fine structure of their cores. The picture of dislocation trails is found to be different in the 1020 μm surface layer that is tentatively ascribed to the near-surface bending of dislocations. In the compressed part, the EBIC and LBIC contrasts are generally smaller and the noticeable DTs are only revealed in the middle part the half-loop. Presumable reasons for the effects are discussed.

Abstract: In silicon several electronic levels are known which can be attributed to transition metals. Ignorance persists however about the specific nature of the defect centers. Some progress was made recently on identifying electronic levels from substitutional or interstitial lattice sites and on identifying levels from defect complexes. The sensitive Laplace DLTS technique allows us to determine depth profiles or the influence of the electrical field on the emission rate with unparalleled accuracy. Three examples will be discussed in this short review: The identification of the CoB pair, a reinterpretation of the Ti DLTS spectrum and the complex formation of interstitial Cu with substitutional Cu as the nucleation site.

Abstract: The reaction of the mobile interstitial Cu_i atom and the A-center (vacancy-oxygen complex) was recently reported to produce at 350 K the rather stable CuVO complex. Chemomechanical polishing in a copper-contaminated slurry allowed to lower the copper in-diffusion temperature down to 295K. The development of the CuVO complex is shown to proceed via formation of the metastable precursor (CuVO*) which introduces two deep levels in the lower half of the band gap. The CuVO* defect is unstable at room temperature and transforms completely into the CuVO complex by a 30 min anneal at 350 K. The proposed structure for the CuVO* complex of a Cu_i atom trapped nearby the A-center is supported by recent ab-initio calculations.

Abstract: Results of a DLTS study on the deep-level centers in the copper-contaminated electron-irradiated FZ-Si are presented. Copper was diffused from the Cu-contaminated surface into previously irradiated samples at 350 K. The most abundant Cu-related complexes formed due to this procedure are the same as in the case of previously studied Cu-diffused Cz-Si.

Abstract: The Czochralski-grown silicon crystals plastically deformed at 680±C to the residual strain of 5% and subsequently annealed in the temperature range of 650{850±C were studied by the IR absorption and DLTS techniques. The formation and disappearance kinetics were investigated for several weak IR absorption lines around the 1000 cm¡1 wave number, which were previously related to the deformation-induced defects of non-dislocation nature in the dislocation trails. In parallel, the spectrum and concentrations of the deep-level centers in the upper half of the gap were measured by DLTS. It is found that the deep-level centers and op- tically active defects exhibit a common behavior during the post-deformation heat treatments. However, a direct correspondence between the IR and DLTS features cannot be established be- cause of the higher concentration of the deep-level centers as compared to the optically active defects.

Abstract: The IR absorption spectra and kinetics of the oxygen solid solution decay were studied in the Si1¡xGex crystals (0 · x · 0:055) plastically deformed at 680±C up to the 2{5% residual strain. It is found that the defects of non-dislocation nature, the dislocation trails, are formed during the plastic deformation of all studied SiGe crystals. The ¯ne structure of the IR absorption spectra around the 1000 cm¡1 wave number is found to be nearly identical in the pure Si (no Ge) samples and Si1¡xGex crystals with x · 0:02. At higher x the ¯ne structure was not detected due to the alloy-related broadening. In all studied crystals, the decay of the supersaturated oxygen solid solution at 650±C is determined by oxygen agglomeration at the dislocation trails as shown by the comparison with the samples annealed at 1150±C.