Light-Induced Degradation of the Carrier Lifetime in n-Type Czochralski-Grown Silicon Doped with Boron and Phosphorus

Abstract

The carrier lifetime in oxygen-rich boron-doped crystalline silicon degrades under illumination at room temperature, both in pand n-type silicon. While this so-called light-induced degradation has been intensely studied in p-type silicon, the data base on n-type silicon is still sparse. In this work, the defect generation in dopantcompensated n-type silicon is investigated at different light intensities, revealing a considerable increase of the defect generation rate with increasing light intensity. Based on this finding, we propose that the defect generation rate constant is proportional to the square of the hole concentration. Since holes are minority carriers in n-type silicon, their concentration depends on the carrier lifetime and the generation rate of excess carriers. The lifetime in turn depends on the amount of recombination active defects, which increases during the course of degradation. The result is a complex time dependence of the effective defect concentration. Simulations based on this model yield excellent agreement with the experimental data. In addition, by comparison with existing data of the rate coefficients in p-type silicon, the defect is identified as the fast forming recombination-center observed in p-Si.