The influence of defect clusters on redistribution of doping impurities in n-and p-type Si0.7Ge0.3 irradiated by reactor neutrons

Samples of a silicon-germanium solid solution with n-and p-type conductivities and resistivities of 1–2×10−3 Ω · cm doped with a natural mixture of phosphorus and boron isotopes were studied while being irradiated in the reactor core of the VVR-M reactor at temperatures in the range 200–500 °C. By using effective-medium theory it is possible to calculate the dose dependence of the resistivity and thermoelectric power of these samples in detail under conditions where clusters can act as effective nuclei for condensation of the doping impurities. Volumes are determined within which clusters can trap doping boron and phosphorus impurities during irradiation, and mean-statistical radii are calculated for the defect clusters and cross sections for their incorporation. It is shown that precipitation of phosphorus primarily decreases the concentration of carriers in a conducting host of the sample during irradiation, while trapping of boron changes the concentration of carriers in the clusters.