Characteristics of formation and annealing of radiation defects in Si in the case of interaction between defects and the surface

A study was made of bulk n-type Si crystals (rho0roughly-equal1Ω x cm)= prepared by zone melting and by the Czochralski method, and of epitaxial films of the 1.2 KEF-1.0/400 KDB-10 grade. Both bulk and films samples were irradiated at T< or =50 0C with 640-MeV protons. An analysis was made of the temperature dependences of the Hall coefficient and of the distributions across the thickness of the majority carrier density and of the concentration of radiation defects formed during various stages of irradiation or 15-min isochronous annealing. A comparison of the results obtained for the bulk crystals with those found for epitaxial Si films of thickness comparable with the diffusion length of radiation defects under the experimental conditions established that in the latter case the influence of the surface on the processes of formation and annealing of radiation defects was manifested clearly by the following effects: 1) a reduction in the rate of formation of the E centers during irradiation of the initial rate of removal of carriers because of the effective loss of vacancies at the surface; 2) an increase in the temperature interval in which the E centers were annealed and a shift of this interval toward lower temperatures; 3) strong accumulation of multivacancy acceptor complexes during annealing (T>400 0C). These results were explained by allowing for the interaction between radiation-generated defects or those migrating during annealing and the surfaces of the samples under the action of elastic stresses and electrical potentials created by the surface