Electrically active light-element complexes in silicon crystals grown by cast method

Abstract

Electrically active light-element complexes called thermal donors and shallow thermal donors in silicon crystals grown by the cast method were studied by low-temperature far-infrared absorption spectroscopy. The relationship between these complexes and either crystal defects or light-element impurities was investigated by comparing different types of silicon crystals, that is, conventional cast-grown multicrystalline Si, seed-cast monolike-Si, and Czochralski-grown Si. The dependence of thermal and the shallow thermal donors on the light-element impurity concentration and their annealing behaviors were examined to compare the crystals. It was found that crystal defects such as dislocations and grain boundaries did not affect the formation of thermal or shallow thermal donors. The formation of these complexes was dominantly affected by the concentration of light-element impurities, O and C, independent of the existence of crystal defects.

Distribution of light-element impurities in Si crystals grown by seed-casting method

“…Control of these light-element impurities, i.e., interstitial oxygen (O i ) and substitutional carbon (C s ), has become essential because light-element impurities affect solar sell performance through defect formation. [17][18][19][20][21][22][23][24][25][26][27] It is necessary to accurately clarify the mechanism of generation of the light-element impurities in Si crystals grown by the seed-casting method to develop methods to suppress the degradation in solar cell efficiency.…”