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 (V_2) to divacancy-oxygen (V_2O) 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 × 10~(15) cm~(-3) and oxygen content of 7.0 ± 1.5 × 10~(17) cm~(-3), have been irradiated with 1.8 MeV protons. Isothermal annealing at temperatures in the range of 200℃-300℃ shows a close to one-to-one correlation between the loss in the donor state of V_2 and the formation of the donor state of V_2O, located at 0.23 eV above the valence band edge. A concurrent transition takes place between the single acceptor states of V_2 and V_2O, 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 V_2 in the studied p-type samples is determined to be (1.5 ± 0.7) × 10~(-3)exp[-(1.31 ± 0.03) eV/kT] cm~2/s, and this represents the neutral charge state of V_2. Further, the data seem to favor a two-stage diffusion mechanism involving partial dissociation of V_2, although a one-stage process cannot be fully excluded.