Grown-in defects limiting the bulk lifetime of p -type float-zone silicon wafers

We investigate a recombination active grown-in defect limiting the bulk lifetime (τ_bulk) of high quality float-zone (FZ) p-type silicon wafers. After annealing the samples at temperatures between 80°C and 400°C, τ_bulk was found to increase from ∼500μs to ∼1.5ms. By isochronal annealing the p-type samples between 80°C and 400°C for 30 min, the annihilation energy (E_ann) of the defect was determined to be 0.3<E_ann<0.7eV. When the annihilated samples were phosphorus gettered at 880°C or subject to 0.2 sun illumination for 24h, τ_bulk was found to degrade. However, when the samples were subsequently annealed at temperatures between 250 and 400°C, the defect could be re-annihilated. The experimental results suggest that the defect limiting the lifetime in the p-type FZ silicon is not related to fast diffusing metallic impurities but rather to a lattice-impurity or an impurity-impurity metastable defect.