Oxygen precipitation in nitrogen doped Czochralski silicon wafers. I. Formation mechanisms of near-surface and bulk defects J. Appl. Phys. 96, 3255 (2004) Heterogeneous iron precipitation in silicon was studied experimentally by measuring the gettering efficiency of oxide precipitate density of 1 ϫ 10 10 cm −3 . The wafers were contaminated with varying iron concentrations, and the gettering efficiency was studied using isothermal annealing in the temperature range from 300 to 780°C. It was found that iron precipitation obeys the so-called s-curve behavior: if iron precipitation occurs, nearly all iron is gettered. For example, after 30 min annealing at 700°C, the highest initial iron concentration of 8 ϫ 10 13 cm −3 drops to 3 ϫ 10 12 cm −3 , where as two lower initial iron concentrations of 5 ϫ 10 12 and 2 ϫ 10 13 cm −3 remain nearly constant. This means that the level of supersaturation plays a significant role in the final gettering efficiency, and a rather high level of supersaturation is required before iron precipitation occurs at all. In addition, a model is presented for the growth and dissolution of iron precipitates at oxygen-related defects in silicon during thermal processing. The heterogeneous nucleation of iron is taken into account by special growth and dissolution rates, which are inserted into the Fokker-Planck equation. Comparison of simulated results to experimental ones proves that this model can be used to estimate internal gettering efficiency of iron under a variety of processing conditions.
We demonstrate that n-type black silicon can be passivated efficiently using Atomic Layer Deposited (ALD) Al 2 O 3 , reaching maximum surface recombination velocities below 7 cm/s. We show that the low surface recombination velocity results from a higher sensitivity of the nanostructures to surface charge and from the absence of surface damage after black silicon etching. The surface recombination velocity is shown to be inversely proportional to the fourth power of the negative charge in contrast to the quadratic dependence observed in planar surfaces. This effect compensates the impact of the increased surface area in the nanostructures and extends the potential of black silicon for instance to n-type Interdigitated Back Contact (IBC) cells.
We investigate the impact of copper on the light induced minority-carrier lifetime degradation in various crystalline silicon materials. We demonstrate here that the presence of neither boron nor oxygen is necessary for the degradation effect. In addition, our experiments reveal that copper contamination alone can cause the light induced minority-carrier lifetime degradation.
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