Vacancy formation energy in Czochralski-grown Si crystals determined by a quenching method

Abstract

The vacancy formation energy in Czochralski-grown (Cz-) Si crystals was determined by applying a new quenching method. In this method, the optical absorption due to hydrogen atoms bound to vacancies is measured to estimate the vacancy concentration. In contrast with floating-zone grown Si crystals, one more optical absorption peak other than 2223 cm−1 peak was observed at about 2120 cm−1. The defects responsible for the 2120 cm−1 peak are proposed to be VOH4 and VO2H4, inferring from the Voronkov-Falster model on grown-in defects in Cz-Si crystals. The vacancy formation energy estimated from the quenching temperature dependence of the integrated intensity of the 2120 cm−1 peak is about 2.3 eV. After taking the contribution from vacancies generated in the perfect crystal part into account, the formation energy is determined to be approximately 1.5 eV. Such small formation energy compared to that (3.85 eV) in high-purity crystals is thought to be due to a strong interaction between a vacancy and an oxygen atom.