Lifetime and DLTS studies of interstitial Fe in p-type Si

Fe is one of the most prominent metallic impurities in solar‐grade Si. In this work we have investigated the kinetics of in‐diffusion and formation of the interstitial fraction (Fei). P‐type Cz‐Si with a resistivity of 10 Ω‐cm has been intentionally contaminated with Fe by in‐diffusion from a surfac...

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Veröffentlicht in:Physica status solidi. C 2011-03, Vol.8 (3), p.721-724
Hauptverfasser: Syre, M., Monakov, E., Holt, A., Svensson, B. G.
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Sprache:eng
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Zusammenfassung:Fe is one of the most prominent metallic impurities in solar‐grade Si. In this work we have investigated the kinetics of in‐diffusion and formation of the interstitial fraction (Fei). P‐type Cz‐Si with a resistivity of 10 Ω‐cm has been intentionally contaminated with Fe by in‐diffusion from a surface layer of FeCl3 at 700 °C followed by cooling with a rate of ∼ 3.3 K/s. The concentration of Fei has been measured both by microwave photo conductance decay (μ‐PCD) and deep level transient spectroscopy (DLTS). In the μ‐PCD measurements, the Fei concentration has been determined using the ef‐ fect of light‐induced splitting of the iron‐boron pairs (FeB), while in the DLTS measurements Fei has been monitored by the donor electronic state at 0.43 eV above the valence band. We have observed a linear dependence between the minority carrier lifetime (τ) and the inverse Fei concentration. This confirms Fei as the dominating recombination centre. In the present investigations we use a material relevant for solar cells with a resistivity of 10 Ω‐cm. We have found that the concentration of interstitial iron decreases with increasing time for in‐diffusion of Fe, provided identical cooling condition. This decreasing con‐ centration of Fei is believed to be due to formation of more iron precipitates that serve as sinks for fast diffusing Fei. A high temperature anneal at 1000 °C for 1 minute followed by fast cooling (∼ 33 K/s) results in dissolution of the precipitates and freezing Fe into interstitial positions, where the concentration of Fei increases with increasing in‐diffusion time. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
ISSN:1862-6351
1610-1642
1610-1642
DOI:10.1002/pssc.201000256