On the electrical activity of oxygen in silicon

Results of Hall effect measurements are given on the electrical activity of oxygen in silicon due to heat treatment at 450 °C. The so-called thermal donor is shown to exhibit two donor states. The thermal ionization energy of the deep donor after short-time heat treatment amounts to E2 = = (135 ± 5) meV, for the shallow donor it is E1 = (61 ± 1) meV. E1 is found to continuously decrease with increasing duration of heat treatment. For example, after 1000 h at 450 °C and for an oxygen concentration of 1.1 × 1018 cm−3 a value of E1 = (18 ± 1) meV is obtained. The temperature dependence of the Hall mobility yields no change of the acceptor concentration with heat treatment. For short duration of heat treatment the temperature dependence of the charge carrier concentration can be described assuming a model of two independent donors or a model of non-He-like divalent donor. For longer duration of heat treatment the properties of thermal donors are more complicated due to the forming of larger complexes.