Beneficial Effect of Two-Step Annealing via Low Temperature of Vacancy Complexes in N-type Czochralski Silicon

We report a simple, time-saving and effective low-temperature approach to avoid the effect of intrinsic defects in n-type Czochralski silicon (Cz-Si) wafers. This approach consists of submitting Cz-Si wafers to two annealing steps. The first annealing step was conducted in the temperature range 100–200°C to dissociate phosphorus–vacancy (P-V) defects. These defects were identified through the calculation of its activation energy (Ea) of annihilation. The second annealing step was conducted in the temperature range 300–400°C to eliminate defects caused by vacancy–oxygen (V-O) pairs. The deactivation effect of the V-O pairs was highlighted using Fourier transform infrared spectroscopy and the effective minority carrier lifetime (τeff). By combining these two annealing steps, we succeeded in enhancing τeff from 180 to 2400 μs and the electrical parameters of the silicon solar cell.