Diffusion-Limited Annealing of Radiation Damage in Germanium

Abstract

The theory of the previous paper in this journal was used to treat the annealing of radiation damage in $n$-type germanium as studied by Fletcher, Brown, and Wright, and by Augustyniak. The damage was produced by 3-Mev electrons to a density of ${10}^{15}$ defects per cubic centimeter. The damage was assumed to have consisted of vacancy-interstitial pairs which annealed by the diffusion together of interstitials and vacancies. A reasonable fit of the data has been obtained for the initial 50% of the annealing. The data of Augustyniak were fit for all stages of the annealing process. Choice of parameters to fit the data led to the following conclusions: (1) The sum of the diffusion coefficients of interstitials and vacancies is given by ${10}^{11}$ ${{r}_{0}}^{2}\mathrm{exp}(\ensuremath{-}31.6 \mathrm{kcal}/RT)$, where ${r}_{0}$ is the capture radius; (2) the average separation of the interstitial and the vacancy of the pairs produced by 3-Mev electrons is approximately 1.5 ${r}_{0}$, and (3) the first 65% of the annealing occurs by the recombination of each interstitial with the vacancy from which it was originally dislodged. Fair agreement of the activation energy with the previously accepted activation energy for vacancy diffusion suggests vacancy-diffusion annealing. Absence of a more rapid interstitial diffusion indicates that the interstitial does not possess the contracted electron cloud of a positive ion.