Papers by Author: O.F. Vyvenko

Abstract: The results of investigations of solar grade mc-Si by means of combination of scanning X-ray beam excited optical luminescence microscopy (SXEOL), X-ray beam induced current (XBIC) and X-ray fluorescence (XRF) are presented. It was found, that for relatively clean sample SXEOL and XBIC provide similar information about the recombination activity of defects while for the samples with a high transition metal content there are significant differences in the provided information. The reasons of the revealed XBIC - SXEOL differences are discussed.

Abstract: The results of experimental investigations of the dislocation-related DLTS-peaks originated from the dislocation networks (DN) are presented. Samples with DNs were produced by direct bonding of p-type silicon wafers and no enhancement of oxygen concentration was detected near the DN plane. Origins of the DLTS peaks were proposed and a correlation with the dislocation-related photoluminescence data was established based on known dislocation structure of the samples. Two types of shallow DLTS peaks exhibited Pool-Frenkel effect, which could be linked to the dislocation deformation potential. One of the shallow DLTS peaks was related to straight parts of screw dislocations and another - to the intersections of the dislocations.

Abstract: Minority carrier diffusion lengths were measured for the set of n- and p-type silicon samples with NiSi2 precipitates of different electronic structure. We found that the type of precipitate electronic states in the upper part of band gap had no influence on the recombination activity of NiSi2 precipitates. Minority carrier diffusion length L was found to be related to the precipitate density N and L ~ 2 × N -1/3 for n-type Si samples and L ~ 1 × N -1/3 for p-Si samples. Hydrogenation of the p-type Si sample with nanoscale nickel silicide precipitates resulted in an increase of the L value up to a factor of 3, while in n-Si L remained practicaly the same. The only hole emission in the samples of both conductivity types was detected in MCTS measurements and the cross section for the hole capture with the electronic states of the precipitaes was estimated to be as large as 10-11 cm-2.

Abstract: Influence of annealing in molecular hydrogen as well as of treatment in hydrogen plasma (hydrogenation) on the electrical properties of NiSi2 precipitates in n- and p-type silicon has been studied by means of deep level transient spectroscopy (DLTS). Both annealing and hydrogenation gave rise to noticeable changes of the shape of the DLTS-peak and of the character of its dependence on the refilling pulse duration that according to [1] allows one to classify the electronic states of extended defects as “band-like” or “localized”. In both n- and p-type samples DLTS-peak in the initial as quenched samples showed bandlike behaviour. Annealing or hydrogenation of n-type samples converted the band-like states to the localised ones but differently shifted the DLTS-peak to higher temperatures. In p-type samples, the initial “band-like” behaviour of DLTS peak remained qualitatively unchanged after annealing or hydrogenation. A decrease of the DLTS-peak due to precipitates and the appearance of the peaks due to substitutional nickel and its complexes were found in hydrogenated p-type sample after removal of a surface layer of 10-20µm.

Abstract: Silicon samples doped with gallium and intentionally contaminated with iron have been studied by means of electron beam current (EBIC), capacitance voltage (CV) and deep level transient spectroscopy (DLTS) methods. Reverse bias anneal (RBA) treatments at temperatures of 390-420K were used to move hydrogen and dissolved iron atoms away from the surface. A new procedure was developed to find dislocations lying on desirable depth from the surface and to analyze the depth distribution of their recombination contrast. Iron contaminated dislocations do not noticeably change their recombination activity when kept in an electrical field as high as 104 V/cm at 420K for several hours. This implies a tight binding of iron atoms at dislocations. The binding energy of iron with dislocations seems to be much larger than for Fe-Ga and H-Ga pairs. Low temperature hydrogenation of iron contaminated dislocations does not produce any passivation effect. In opposite, the recombination activity of the dislocations significantly increases after RBA treatment.