Defect and Diffusion Forum Vols. 245-246

Abstract: The dependence of concentration of defects on doping level for average cluster in n-Si was calculated. It was shown that in the framework of the Gossick's model the concentration of defects for the average cluster is in inverse proportion to the square of a cluster radius. One obtains the size distribution of defect clusters created by fast neutrons of WWR-M reactor, by the transformation of energy spectrum of the primary knock-on atom in n-Si (FZ, Cz). Threshold energy of defect clusters formation 4.7 keV by comparing n-Si crystals irradiated by deuterons and fast-pile neutrons was calculated.

Abstract: We present a unified approach to description of all the stages of shaping of a highabsorption state in a resonatorless exciton bistable system, as a nonequilibrium first-order transition. The velocity of switching wave front and thickness of interface between phases are determined within the quick switching wave approximation. The size distribution functions of subcritical and supercritical nuclei and asymptotic expression for nucleus radius were obtained.

Abstract: Dislocations and impurities in silicon have been widely investigated since many years, nevertheless many questions on this subject remain still unsolved. As an example, theory, models and experimental phenomena provide evidence of the existence of shallow bands in silicon induced by the dislocation strain field. Nevertheless, only deep bands, likely associated with contamination at dislocations, have been detected up to now by junction spectroscopy. The present contribution reviews several results, obtained by the authors, on dislocation impurity interactions and their effects on the electronic properties of defect states in silicon. Point and extended defects introduced in p-type Cz Si by oxygen precipitation and plastic deformation have been investigated with electrical methods. Different materials (oxygen precipitated and deformed Cz Si and Fz Si) were examined in order to separate the role of oxygen precipitation, plastic deformation and metallic contamination on non-radiative electronic transitions at defect centers. A deep hole trap, named T1, has been associated to dislocation-related impurity centers, while additional deep traps have been related to contamination by grown-in transition metals and to clusters involving oxygen atoms. Moreover, experimental results obtained by junction spectroscopy assessed the existence of dislocation related shallow states. These were found to be located at 70 and 60 meV from the valence and conduction band edge, respectively.

Abstract: Silicon surface barrier (SSB) detectors have been fabricated with oxygen enriched, high-resistivity, detector grade, n-type FZ silicon. Oxygen enrichment of the wafer was done by high-energy (140 MeV) oxygen ion implantation. Annealing of the irradiated silicon wafer was done to minimize the irradiation-induced defect concentration. Positron annihilation lifetime studies were used to select the annealing temperature. A comparative study was carried out among various SSB detectors made from as-grown, as-irradiated and annealed silicon wafers. Detector made from the annealed wafer worked satisfactorily and its performance was comparable with that of a detector made from as-grown crystal.

Abstract: A cluster comprising of indium, antimony and a vacancy in silicon is analysed using the planewave pseudopotential technique. This cluster has a strong binding energy that inhibits indium diffusion after high temperature anneal cycles. Difficulties associated with the simulation of a vacancy using the supercell approach are initially highlighted. In comparison, the indium-antimony-vacancy cluster reveals stronger distortions and reduction in relaxation volume. The indium atom in the relaxed cluster shows nearly six-fold coordination whereas the antimony atom acquires four neighbours. Due to the low symmetry of the centre, in constrast to the isolated vacancy there is no propensity for a Jahn-Teller effect. It gives rise to two defect levels in the bandgap.

Abstract: In this paper, the following issues: epitaxial growth, boron incorporation and electrical properties of Si1-x-yGexCy layers grown by reduced pressure chemical vapor deposition (RPCVD) are presented. Furthermore, diffusion of carbon and boron in silicon-based material is also discussed.