Comprehensive analysis of the impact of boron and oxygen on the metastable defect in Cz silicon

Two important aspects of the formation mechanism of the metastable defect specific to boron-doped Czochralski silicon (Cz-Si) are investigated in detail. In the first part of the paper the impact of boron and oxygen on the defect formation process is investigated. Lifetime measurements performed on a large number of different silicon materials yield a quadratic dependence of the light-induced metastable defect concentration N/sub t/* on the interstitial oxygen concentration [O/sub i/] for samples with oxygen concentrations greater than 4/spl times/10/sup 17/ cm/sup -3/ while for samples with lower oxygen concentrations the dependence is found to be almost linear. All samples show a linear dependence of N/sub t/* on the substitutional boron concentration. The second part of the paper is devoted to the fast performance loss at the beginning of the degradation process. A thorough analysis of temperature-dependent measurements of the degradation of the open-circuit voltage of Cz-Si solar cells during illumination reveals a two-step mechanism. While the time constant of the fast initial degradation is found to be independent of temperature, an activation energy of 0.37 eV is determined for the slower degradation process.