Re-evaluation of the SRH-parameters for the FeGa defect

Abstract

In this work the existing SRH parametrizations for the FeGa defect are re-evaluated by a deliberately iron contaminated sample set of varied doping densities. The evolution of the cross-over point is analyzed for this aim, due to its characteristic dependency on the defect parameters of the metastable iron states. It can give insight into the defect parameter, whilst being independent of most factors usually limiting evaluations precision. The proposed parameter adjustment provides an improved description of the measurement data compared to the literature parametrizations.

Gallium‐Doped Silicon for High‐Efficiency Commercial Passivated Emitter and Rear Solar Cells

“…Our experiments on this sample set have indicated the presence of interstitial Fe contamination, as we observe an increase in lifetime after illumination (for 20 s at 1 Sun), followed by a slow decay in lifetime when stored in the dark for up to 72 h. This is consistent with the reformation time scales of FeB and FeGa pairs. [ 1,9–11 ] While we have indications that FeGa pairs are forming recombination centers in our Ga‐doped silicon samples, it is difficult to determine the concentration of iron from traditional lifetime measurement techniques (despite our best efforts), as the FeGa pairs apparently never fully dissociate under illumination at room temperature. If we do assume 100% FeGa dissociation post illumination (for 20 s at 1 Sun), our best estimate of the iron concentration is of order 10 9 cm −3 and is consistent with our findings in Figure 2a.…”

“…[ 50 ] Unless otherwise stated, lifetime measurements were taken directly after illuminating the samples for 20 s at 100 mW cm −2 to minimize the impact of iron–gallium recombination centers. [ 9–11 ]…”

“…Published research into lifetime issues associated with gallium‐doped silicon is relatively limited. Although relatively well‐understood lifetime changes occur in gallium‐doped silicon when it is deliberately contaminated with iron [ 7–11 ] or copper, [ 12 ] it is not clear how important these effects are in modern commercial gallium‐doped Cz wafers. Given gallium‐doped silicon's relatively recent transition to commercial importance, research to understand its carrier lifetime limitations is a key research focus.…”