Float-zone crystals of n-type material, with doping levels of between 1.5 x 1014 and 2 x 1016/cm3 and containing some 1018Sn/cm3, were irradiated with 2MeV electrons to various doses and were studied by using deep level transient spectroscopy, Mössbauer spectroscopy and positron annihilation. Two Sn-vacancy levels, at Ec-0.214eV and Ec-0.501eV, were identified. On the basis of investigations of the temperature dependence of the electron capture cross-sections, the electric-field dependence of the electron emissivity, the annealing temperature and the defect-introduction rate, it was concluded that these levels were the double- and single-acceptor levels, respectively, of the Sn-V pair. These conclusions were in agreement with electronic structure calculations which were carried out using local spin-density functional theory, which incorporated pseudopotentials in order to eliminate the core electrons, and which were applied to large H-terminated clusters. It was concluded that the Sn-V pair had 5 different charge states, which corresponded to 4 levels in the band-gap.

Tin-Vacancy Acceptor Levels in Electron-Irradiated n-Type Silicon. A.Nylandsted Larsen, J.J.Goubet, P.Mejlholm, J.Sherman Christensen, M.Fanciulli, H.P.Gunnlaugsson, G.Weyer, J.Wulff Petersen, A.Resende, M.Kaukonen, R.Jones, S.Oberg, P.R.Briddon, B.G.Svensson, J.L.Lindström, S.Dannefaer: Physical Review B, 2000, 62[7], 4535-44