Lifetime-degrading boron-oxygen centres in p-type and n-type compensated silicon

Abstract

Degradation of minority carrier lifetime under illumination occurs in boron-containing Czochralski silicon of both p- and n-type. In n-Si, the recombination centre responsible for degradation is found to be identical to the fast-stage centre (FRC) known for p-Si, where it is produced at a rate proportional to the squared hole concentration, p2. Holes in n-Si are the excess minority carriers—of a relatively low concentration; hence, the time scale of FRC generation is increased by several orders of magnitude when compared to p-Si. The degradation kinetics, which is non-linear, due to dependence of p on the current concentration of FRC, is well reproduced by simulations. The injection level dependence of the lifetime shows that FRC exists in 3 charge states (− 1, 0, + 1) possessing 2 energy levels. Comparison of n-Si samples of various electron concentrations shows that FRC emerges by the reconstruction of a latent BsO2 complex of a substitutional boron and an oxygen dimer (while the major recombination centre in p-Si denoted SRC was previously found to emerge by reconstruction of BiO2 defect involving an interstitial boron atom). A model of the BsO2 reconfiguration into FRC through an intermediate state accounts for the rate constant dependence on p, which is reduced to a p2 proportionality, under certain conditions.