EFFECTS OF IRON CONTAMINATION ON THE ELECTRICAL-ACTIVITY OF A SILICONBICRYSTAL

Experiments of electron-beam-induced current (EBlC) and deep-level tra nsient spectroscopy have been performed on a Sigma = 25 silicon bicrys tal precontaminated with Fe and then annealed at 1200 degrees C. Contr ary to ail other similarly heat treated samples, whether they are as-r eceived or deliberately contaminated with the fast diffusing Cu and/or Ni, the slowly cooled sample containing Fe exhibited an enhanced EBIC contrast and barrier effects at the grain boundary level, which have been associated with the formation of iron silicides at the interface. On the other hand, the rapid cooling has been found to 'freeze' the m oderately diffusing Fe in interstitial sites (Fe-i) which act as recom bination centres and are then at the origin of the observed general de crease of the EBIC in the bulk. A specific additional treatment of the quenched samples has led to the restoration and even improvement of b oth the EBIC signal and the minority carrier diffusion length.