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The behavior of iron, iron-boron (FeB) pairs, and iron-boron-phosphorus (FeB-P) complexes has been studied in B-doped Czochralski silicon with phosphorus (P) compensation and compared with that in uncompensated material. The interstitial iron concentration has been measured at temperatures from 50 to 270°C. The apparent binding energy (

Low-cost silicon feedstock for photovoltaic (PV) industry contains dopant species and metal impurities, in most cases boron (B), phosphorous (P), and iron (Fe) [

At temperatures below 100°C, the formation of FeB is the dominant process in uncompensated material, while a recovery of ^{16} cm^{−3}, however, the temperature must be higher than 300°C in uncompensated Si [

In this letter, the effect of dopant compensation in silicon on the behavior and properties of Fe is investigated at temperatures between 50 and 270°C. The concentration of single positively charged interstitial iron atoms

1 × 1 cm^{2} p-type ^{16} cm^{−3}. The second set of samples (labeled CZ-2) is B and P codoped, with ^{16} cm^{−3} and P concentration (^{16} cm^{−3}, as determined by secondary ion mass spectroscopy (SIMS). The interstitial oxygen concentration in all the samples is about 10^{18} cm^{−3}, as determined by Fourier transform infrared spectroscopy (FTIR) using the 3.14 × 10^{17} cm^{−2} calibration factor. After dipping in 0.1 mol/L ferric nitric acid (Fe(NO_{3})_{3}) solution, Fe was diffused into the samples by annealing in an argon ambient at 800°C for 2 h, followed by quenching in air. Fe concentration that can be introduced into the samples at that temperature is of the order of 10^{12} cm^{−3} according to the solubility of iron in silicon [

It is well known that association and dissociation of FeB in silicon are reversible, which can be expressed by [^{13} ^{−3} for the WT2000 instruments as determined from the recombination parameters of ^{16} cm^{−3} [^{12} cm^{−3} and (6.2 ± 0.1) × 10^{12} cm^{−3} for compensated and uncompensated silicon, respectively, as shown in Figure ^{13} cm^{−3} and (1.4 ± 0.1) × 10^{13} cm^{−3} for compensated and uncompensated silicon, respectively. Both values are somewhat higher than the estimated solubility which is due to the prefactor

(a) The carrier lifetime as a function of temperature for CZ-1 and CZ-2. (b) The concentration of

Figure ^{0/+}, for all temperatures studied [

The ratio of

In uncompensated material and assuming there are only two carrier recombination centers, that is, ^{22} cm^{−3}), ^{−6} which is close to the theoretical value of 0.9 × 10^{−6} for (^{16} cm^{−3}. As shown in Figure ^{−3} which is three orders of magnitude larger than the value of (^{−6}, since ^{16} cm^{−3}. It illustrates that P codoping with B leads to the creation of different carrier recombination centers, probably besides FeB also FeB-P related complexes. Iron might indeed also form complexes with B-P pairs with a different binding energy than that with B, leading to the observed lower effective binding energy which would be a combination of the binding of FeB and of FeB-P. Substitutional P^{+} close to B^{-} will indeed impact the electrostatic interaction between

The ratio of^{4} and

The ratio of^{−6}

However, the situation is different in compensated silicon, as shown in Figure ^{16} cm^{−3}/4.10 × 10^{16} cm^{−3}). This illustrates once more that, besides the recombination centers related to FeB and

The ratio of^{−3}^{−5}^{−6}

For further support of the above mentioned model, the binding energy of FeB and FeB-P complexes has been calculated using the density-functional theory (DFT). All calculations were performed with the Vienna ab initio simulation package (VASP) [^{−5} eV. Finally, the GGA +

In summary,

The authors declare that there is no conflict of interests regarding the publication of this paper.

This project is supported by the National Natural Science Foundation of China (nos. 51532007, 61574124, and 61274057), and the authors are also grateful to Professor Duanlin Que for his supervision.

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