On the equilibrium concentration of boron-oxygen defects in crystalline silicon

determine the equilibrium concentration of the BO defect in boron-doped Czochralski-grown silicon after prolonged (up to 150 h) annealing at relatively low temperatures between 200 and 300 degrees C. We show that after sample processing, the BO concentration has not necessarily reached the equilibrium state. The actually reached state depends on the detailed temperature profile of the last temperature treatment before the light-induced degradation (LID) is performed. For the investigated Cz-Si materials with base resistivities ranging between 0.5 and 2.5 Omega cm, we observe that an annealing step at 200 degrees C for 50 h establishes the equilibrium, independent of the base resistivity. Experiments performed at different temperatures reveal that the equilibrium defect concentration decreases with increasing annealing temperature. This observation can be understood, assuming a mobile species which is distributed between at least two different sinks. A possible defect model is discussed.