Investigation of point defects in silicon and germanium by non-irradiation techniques

Abstract

The paper reviews the information on vacancies and interstitials from such techniques as diffusion studies, precipitation from supersaturated solid solutions, quenching from high temperatures, and plastic deformation. Self- and impurity diffusion are considered in some detail and the evidence is presented according to which the high-temperature self-diffusion occurs via extended interstitials in silicon and via extended vacancies in germanium. From the diffusion coefficients of group-V impurities and from the precipitation of substitutional nickel impurities the selfdiffusion coefficient for a vacancy self-diffusion mechanism is derived and found to be lower than that from high-temperature self-diffusion experiments. This constitutes evidence for a change-over in the self-diffusion mechanism in silicon at about 900 °C to a low-temperature vacancy mechanism with lower activation energy and lower preexponential factor than the interstitial mechanism. It is proposed that self-interstitials in silicon might have a rather high migration energy, E ^1I,^M; tentatively; E ^{1I M} ⋍ 0.8 eV and a donor level at 0.40 eV above the valence band are attributed to the self-interstitials in silicon.