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

摘要

The formation of the divacancy-oxygen centre (V _2O) in p-type Czochralski-grown silicon has been investigated by means of deep level transient spectroscopy (DLTS). The donor state (+/0) of V _2O is located at ～E v+0.23eV (E _v denotes the valence band edge) and emerges during heat treatment above 200°C at the expense of the divacancy centre (V _2). A concurrent transition takes place between the single-acceptor states of V _2 and V _2O, 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 ～E _v+0.09eV evolves in close correlation with the growth of V _2O but at a factor of ～5-6 lower in concentration. In the literature, the E _v+0.09eV level has previously been attributed to a double-donor state of V _2O but this assignment can be ruled out by the present data favouring a complex formed between migrating V _2 centres and a competing interstitial oxygen trap. In addition, a level at ～E _v+0.24eV occurs also during the heat treatment above 200°C and is tentatively assigned to the trivacancy-oxygen centre (V _3O).