Minority carrier lifetime degradation induced by illumination was studied in n-type Czochralski silicon co-doped with phosphorus and boron. The recombination centre that emerges during the degradation was found to be identical to the fast-stage centre (FRC) which is known for p-Si where it is produced at a rate proportional to the squared hole concentration, p~2. In n-type material where holes are excess carriers of a relatively low concentration, the time scale of FRC generation in n-Si is increased by several orders of magnitude. The generation kinetics is non-linear as a result of the dependence of p on the concentration of FRC. This non-linearity is well reproduced by simulations. An analysis of the injection level dependence of the minority carrier lifetime shows that FRC exists in 3 charge states (-1, 0, +1) possessing 2 energy levels. The recombination is controlled by both levels. FRC is identified as a B_8O_2 complex of a substitutional boron and an oxygen dimer. The nature of the major lifetime-degrading centre in n-Si is thus different from that in p-Si - where the dominant one (a slow-stage centre, SRC) was found to be B_iO_2 - a complex involving an interstitial boron.
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