Carrier recombination in silicon is analyzed as a function of doping density. Two mechanisms are identified: one for the low concentration range and one, of the Auger type, for the high concentration range. Disagreements with the theoretical predictions for the Auger process are discussed and empirical laws connecting lifetime to dopant concentration are determined.

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The correlation between minority carrier lifetime and deep-level transient spectroscopy measurements was used in order to obtain more information about the mechanisms of defect formation and annealing in CZ and FZ silicon during high temperature heating by lamp. Different energy levels induced by lamp annealings were detected: a good correlation with the lifetime behavior was observed for a donor at Ev + 0.29 eV. No direct influence of the oxygen content was detected at 1050~ while at 750~ a gettering action of oxygen aggregates can be hypothesized.

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Thermal induced defects in high quality FZ silicon are studied. The principal aim of the work is to clarify the influence of dopant concentration on their generation and to observe the behaviour of carbon and residual impurities like heavy metals in the presence of very low oxygen contents. For low temperature heatings the most important mechanism responsible for lifetime deterioration in lightly and moderately doped silicon (cB < 1017 cm−3) is tentatively identified as FeB pair dissociation. At higher temperatures other mechanisms, like those associated with defect formation by thermal stresses and accidental contamination, can act, thus modifying the final effects on lifetime. For boron content higher than 1017 cm−3, heat treatments have only little effects on electrical parameters and crystal perfection of FZ silicon. Carbon (at the concentration commonly available in commercial high quality FZ silicon) do not have any direct influence on wafer annealing behaviour.