EPR studies of silicon irradiated at 20.4 K and 4.2 K by 1.5 MeV and 46 MeV electrons are described. In 46 MeV irradiations the dominant defects formed appear to be divavancies and other multiple defect aggregates which liberate vacancies throughout the anneal to room temperature as they reorder, recombine, etc. For 1.5 MeV irradiations group III atoms play a vital role in p- and n-type materials in trapping interstitials and stabilizing damage. Carbon and oxygen are not effective interstitial traps at these temperatures. Evidence of limited vacancy migration during irradiation is also cited. Two distinct excited configurations of vacancy-oxygen pairs are identified as precursors to A-centre formation in n-type silicon. The kinetics for their conversion to A-centres depends strongly upon the Fermi level as does the isolated vacancy migration energy whhich is measured to be 0.18 ± 0.02 eV for the V^＝ charge state. The vacancy has four charge states, V^＋, V⁰, V^－ and V^＝. Kinetics for hole release from V^＋ reveals an activation barrier of 0.057 eV. The concentration of V^＋ at 20.4 K in boron-doped material indicates the corresponding donor level even closer to the band edge, approximately E_V ＋ 0.039 eV. Jahn-Teller energies for V⁰, V^＋, and V^－ are estimated from stress-alignment studies and confirmed to be large. Kinetics studies for reorientation from one Jahn-Teller distortion to another are also described for each charge state.

A rich variety of optical centers with high energy local vibrational modes has been found in electron-irradiated 4H-SiC in both the as-irradiated and annealed states. These energies have been measured and the annealing dependence of the optical centers has been investigated by low-temperature... (Read more)

The electronic, structural, and vibrational properties of small carbon interstitial and antisite clusters are investigated by ab initio methods in 3C- and 4H-SiC. The defects possess sizable dissociation energies and may be formed via condensation of carbon interstitials, e.g.,... (Read more)

The migration of monovacancies (V⁰) and self-interstitials (I) has been observed in ion-implanted low-doped float-zone silicon by variable-energy positron annihilation spectroscopy. V⁰ and I were created by the in situ implantation of ~20 keV... (Read more)