The formation energy and thermal equilibrium concentration of vacancies in Ge doped Czochralski-grown Si are studied by quenching of samples annealed at temperatures between 1200 and 1350°C for 1 h under hydrogen atmosphere. After quenching, the majority of the formed vacancy and hydrogen containing point defect clusters are transformed into VH 4 defects by a 1 h anneal at 450°C. Measuring the amplitude of the vibrational band of VH 4 at 2223 cm −1 as function of the quenching temperature

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... estimating the vacancy formation energy. An apparent formation energy of about 2 eV is obtained for Ge doping between 7 ϫ 10 17 and 6.5ϫ 10 20 cm −3 which is significantly lower than the 4 eV obtained for high purity Si. In the whole quenching temperature window, the vacancy thermal equilibrium concentration is significantly higher than in Si without Ge doping. It is shown that this lower apparent formation energy can be explained by the presence of vacancy traps.