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The technical assistance of Dave Elliott and Sylvain Laframboise and stimulating discussions with Ernie Kornelsen are acknowledged. SIMS measurements made using the CAMECA 3F facilities of Surface Western with the assistance of Garry Mount and the CAMECA 4F facilities of CANMET with the assistance of Jennifer Jackman.

Deep level transient spectroscopy and double correlation technique were used to examine the annealing and profiles of interstitial iron in boron-doped silicon at a temperature range from 50 to 400 °C. The results show that iron-boron pairs begin to break-up at a temperature as low as 50 °C. After a short time annealing (5 min) at a temperature up to 400 °C, most of the iron from the breaking is converted into interstitial iron. We also find that the distribution of interstitial iron under the silicon surface is not uniform, and it depends on the annealing time and temperature. The interstitial iron near the silicon surface decreases with the increase of the annealing time.

Polycrystalline silicon has been deposited on low-cost graphite substrates by the thermal decomposition Of silane and thermal reduction of trichlorosilane with hydrogen in a gas flow system. The microstructures and crystallographic properties of deposited silicon were studied over a wide range of deposition conditions by metallographic and x-ray techniques, respectively. The observed differences in the properties of silicon layers deposited by silane and trichlorosilane processes were attributed to the difference in the chemical reversibility of the reactions. The microstructure of silicon deposited by the trichlorosilane process was improved by the addition of hydrogen chloride to the reactant mixture. Solar cells were prepared from silicon layers deposited on graphite substrates by a one-step process using silane or trichlorosilane and appropriate dopants, and AMO efficiencies of up to 1.5% were obtained.The current interest in the terrestrial utilization of solar energy by photovoltaic converters has stimulated considerable research and development efforts in lowcost solar cells. Silicon solar cells which have been used reliably in spacecrafts for many years are manufactured from semiconductor-grade silicon and are far too expensive for terrestrial applications. The use of polycrystalline silicon layers on suitable substrates is considered as a promising approach for the fabrication of low-cost solar cells (1). In this approach, the selection of the substrate is an important consideration. Steel is the most economical choice for a large area substrate; however, polycrystalline silicon solar cells deposited on steel substrates were found to have low conversion efficiencies because of the incompatibility of the properties of iron and silicon (2). Graphite is more compatible with silicon in properties than steel. Several types of low-cost graphite have a thermal expansion coefficient similar to that of silicon. Graphite is relatively inert toward silicon at temperatures used for the deposition of silicon. Also, graphite has high thermal and electrical conductivities and may be used as an ohmic contact to the solar cell. Thus, graphite appears to be the most promising substrate for low-cost silicon solar cells at present.In this work, the thermal decomposition of silane and the thermal reduction of trichlorosilane with hydrogen have been used for the deposition of silicon on graphite substrates. The microstructure and crystallographic properties of silicon deposited under a wide range of conditions were studied. Using appropriate dopants during the deposition process, p-n junction solar cell structures were prepared and characterized. The experimental procedures used for the deposition process and the properties of deposited silicon and solar cells are discussed in this paper.