Papers by Author: Vitaly V. Kveder

Abstract: The efficiency of solar cells produced from crystalline silicon materials is considerably affected by the presence of metal impurities. In order to reduce the concentration of metal impurities, gettering processes as phosphorus diffusion gettering (PDG) and aluminum gettering (AlG) are routinely included in solar cell processing. Further development and optimization of gettering schemes has to ground on physics-based simulations of gettering processes. In this contribution we use quantitative simulations to compare the efficiency and kinetics of PDG and AlG in the presence of precipitates for interstitially dissolved metals, like iron, at different gettering conditions. Recently measured segregation coefficients of iron in liquid AlSi with respect to crystalline silicon are used in order to compare with PDG under typical conditions. It is shown that kinetics of both, PDG and AlG, can be separated into two regimes: (i) at low temperatures kinetics are limited by precipitate dissolution, and (ii) at high temperatures kinetics of AlG is mainly limited by metal impurity diffusion while phosphorus in-diffusion is the limiting factor of PDG.

Abstract: There is a growing demand for a silicon-based light emitters generating a light with a wavelength in of 1.3-1.6 μm range, which can be integrated into silicon chips and used for in-chip opto-electronic interconnects. Among other possibilities, the D1 luminescence at about 1.55 m, caused by dislocations in Si, can be a suitable candidate for such in-chip light emitters. Here we present a brief review of today knowledge about electronic properties of dislocations in silicon and dislocation-related luminescence in connection with possible application of this luminescence for silicon infrared light-emitting diodes (Si-LEDs).

Abstract: We investigated the development of dislocation-related DLTS spectra in n-CZ-Si crystals with small (about 7.104 cm-2) number of long individual dislocations depending on the distance L that dislocations traveled during deformation at 600oC and on the velocity of dislocations. We found that a typical dislocation-related DLTS signal appeared only when dislocations traveled a significant distance that is more than 150-200μm, and it depended strongly on dislocation velocity. The results were interpreted on the assumption that the DLTS signal corresponds to some core defects and atomic impurities accumulated on the dislocations during their slow motion. At high concentration of deep level defects on dislocations a strange “negative DLTS” signal was observed. This can be explained by electron tunneling between deep defects along dislocations.

Abstract: The paper describes the elaboration of a method for producing composite Si/SiC wafers and investigation of their properties. The known two-shaping elements (TSE) method was used to produce the material. Pilot tests show that this composite material can be used for production of solar cells. The structure of silicon grains is elongated relative to the growth direction, the dislocation density in grains is of about (5÷8) ×104 cm-2, the average lifetime of minority carriers is 4÷6 µs.

Abstract: We investigated the effect of magnetic field on the unlocking stress for dislocations in Cz-Si, measured at 600oC, depending on the thermal prehistory of samples. The effect increases with increasing of the duration of sample annealing at 600oC before the magnetic field treatment. The experimental data are consistent with the assumption that the magnetic field stimulate some changes in configuration of oxygen accumulated at dislocations before the magnetic field treatment, but not the state of oxygen in a bulk.

Abstract: Deep electronic states associated with iron silicide precipitates have been studied by means of deep-level transient spectroscopy. The observed spectra show the characteristic features of bandlike states at extended defects. From the stability of the states on annealing at moderate temperature they are tentatively attributed to precipitate-matrix interfaces.