Transformation of divacancies to divacancy-oxygen pairs in p-type Czochralski-silicon; mechanism of divacancy diffusion

摘要

In this work, a comprehensive study on the transition of divacancy (V2) to divacancy-oxygen (V2O) pairs in p-type silicon has been performed with deep level transient spectroscopy (DLTS). Czochralski grown, boron doped p-type, silicon samples, with a doping concentration of 2 × 1015 cm−3 and oxygen content of 7.0 ± 1.5 × 1017 cm−3, have been irradiated with 1.8 MeV protons. Isothermal annealing at temperatures in the range of 200 °C–300 °C shows a close to one-to-one correlation between the loss in the donor state of V2 and the formation of the donor state of V2O, located at 0.23 eV above the valence band edge. A concurrent transition takes place between the single acceptor states of V2 and V2O, as unveiled by injection of electrons through optical excitation during the trap filling sequence of the DLTS measurements. Applying the theory for diffusion limited reactions, the diffusivity of V2 in the studied p-type samples is determined to be (1.5 ± 0.7) × 10−3exp[−(1.31 ± 0.03) eV/kT] cm2/s, and this represents the neutral charge state of V2. Further, the data seem to favor a two-stage diffusion mechanism involving partial dissociation of V2, although a one-stage process cannot be fully excluded.