Formation of donor and acceptor states of the divacancy–oxygen centre in p-type Cz-silicon

Abstract

The formation of the divacancy–oxygen centre (V2O) in p-type Czochralski-grown silicon has been investigated by means of deep level transient spectroscopy (DLTS). The donor state (+/0) of V2O is located at ∼Ev + 0.23 eV (Ev denotes the valence band edge) and emerges during heat treatment above 200 °C at the expense of the divacancy centre (V2). A concurrent transition takes place between the single-acceptor states of V2 and V2O, as unveiled by the injection of electrons through optical excitation during the trap filling sequence of the DLTS measurements. Further, a defect with an energy level at ∼Ev + 0.09 eV evolves in close correlation with the growth of V2O but at a factor of ∼5–6 lower in concentration. In the literature, the Ev + 0.09 eV level has previously been attributed to a double-donor state of V2O but this assignment can be ruled out by the present data favouring a complex formed between migrating V2 centres and a competing interstitial oxygen trap. In addition, a level at ∼Ev + 0.24 eV occurs also during the heat treatment above 200 °C and is tentatively assigned to the trivacancy–oxygen centre (V3O).