LAUSR

Abstract Recently, it has been shown that the investigation of minority carrier traps (traps) is a useful method to study defects in silicon wafers. In this paper, we report the presence of traps in p-type multicrystalline silicon with a photoconductance decay time constant of 1.9 ± 0.4 s (at 30 °C). It is shown that the density of traps is significantly reduced after firing. However, this reduction in trap density is metastable, and it recovers by short dark annealing at 100 °C or after several days of storage at room temperature. In contrast, laser annealing is shown to eliminate the traps in fired wafers, while no change in the trap density is observed for wafers that have not been fired. Further dark annealing of those wafers does not recover the traps, suggesting that this trap annihilation is not reversible.