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a -SiC:H films with energy gap in the range 2.00–2.65 eV have been grown by plasma enhanced chemical vapor deposition in undiluted and H2 diluted SiH4+CH4 gas mixtures, by making use of optimized deposition conditions. A complete picture of structural, compositional, optoelectronic, and defective properties for high quality films has been drawn for the first time. We show that the addition of H2 to the gas mixture leads to a different chemical composition of the deposited films; in particular, carbon incorporation is enhanced and a carbon fraction in the solid matrix up to C/(C+Si)≈0.45 can be obtained. These films have a higher mass density, a reduced microvoid and carbon cluster concentration, a better structural connectivity, and improved optoelectronic properties. For samples with optical gap below 2.4 eV, the reduced defect concentration of H2 diluted films results in an increase of the photoconductivity gain and the steady-state (ημτ)ss values up to two orders of magnitude.

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Supersaturated solutions of substitutional, electrically active Sb in (lOO) silicon single crystals have been obtained by ion implantation, foUowed by short-duration incoherent-light annealing. Substitutional and nonsubstitutional fractions have been studied as functions of implanted dose and anneal temperature by Rutherford backscattering and channeling techniques, transmissionelectron microscopy, Hall-effect and resistivity measurements (combined with layer removal), and Mossbauer spectroscopy. The maximum electrically active concentration, which can be incorporated on undisturbed substitutional sites, is found to be 4.5X 10 20 Sb/cm3 for 700 DC annealing. Upon further annealing, the supersaturated solution is reduced and approaches the Trumbore solubility value at temperatures of about 1100 DC. The Sb going out of solution is shown for the first time to be created in two different surroundings: Sb is predominantly found in Sbvacancy complexes for low doses and low annealing temperatures and in Sb precipitates for high doses and/or high annealing temperatures. Complete agreement is found between substitutional fractions derived from MOssbauer spectroscopy and electrically active fractions from Hall-effect measurements, whereas the substitutional fractions from channeling measurements are significantly higher. The experiments are not conclusive as to whether this difference is due to the fraction of Sb in Sb-vacancy complexes or in coherent Sb precipitates.