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Title: Thin films of silicon on low-cost substrates. Quarterly report No. 5, January 1-March 31, 1978

Abstract

Parametric studies of silicon deposition were conducted employing the horizontal Energy Beam system. Chemical equilibrium calculations pertaining to the Energy Beam deposition conditions were performed. These calculations indicated that the reaction efficiency for hydrogen reduction of silicon tetrachloride is over 95% for any chlorosilane concentration at the Energy Beam temperature of 4300/sup 0/K. Because lower temperatures exist near the substrate surfaces, the kinetics of establishing the low temperature equilibrium will determine obtainable material efficiencies. From deposition experiments, the material efficiency was found to be strongly dependent on input chlorosilane concentrations. The highest material efficiency and growth rate obtained concurrently to date were 70% and 10 ..mu..m/min using the horizontal Energy Beam system. The Thermal Expansion Shear Separation (TESS) process for producing self supporting silicon films was further investigated.

Authors:
; ; ;
Publication Date:
Research Org.:
Motorola, Inc., Phoenix, AZ (USA)
OSTI Identifier:
5749786
Report Number(s):
DOE/ET/20410-T8
ON: DE81029472
DOE Contract Number:
AC03-76ET20410
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; ENERGY BEAM DEPOSITION; EQUILIBRIUM; SILICON; CHEMICAL REACTIONS; CHLORINE COMPOUNDS; EFFICIENCY; FILMS; GRAIN SIZE; HYDROGEN; MORPHOLOGY; REACTION KINETICS; REDUCTION; SILANES; SUBSTRATES; THERMAL EXPANSION; ULTRAHIGH TEMPERATURE; CRYSTAL STRUCTURE; DEPOSITION; ELEMENTS; EXPANSION; HALOGEN COMPOUNDS; HYDRIDES; HYDROGEN COMPOUNDS; KINETICS; MICROSTRUCTURE; NONMETALS; SEMIMETALS; SILICON COMPOUNDS; SIZE; SURFACE COATING; 140501* - Solar Energy Conversion- Photovoltaic Conversion

Citation Formats

Sarma, K.R., Gurtler, R.W., Baghdadi, A., and Cota, M. Thin films of silicon on low-cost substrates. Quarterly report No. 5, January 1-March 31, 1978. United States: N. p., 1978. Web. doi:10.2172/5749786.
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Sarma, K.R., Gurtler, R.W., Baghdadi, A., & Cota, M. Thin films of silicon on low-cost substrates. Quarterly report No. 5, January 1-March 31, 1978. United States. doi:10.2172/5749786.
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Sarma, K.R., Gurtler, R.W., Baghdadi, A., and Cota, M. Sun . "Thin films of silicon on low-cost substrates. Quarterly report No. 5, January 1-March 31, 1978". United States. doi:10.2172/5749786. https://www.osti.gov/servlets/purl/5749786.
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@article{osti_5749786,
title = {Thin films of silicon on low-cost substrates. Quarterly report No. 5, January 1-March 31, 1978},
author = {Sarma, K.R. and Gurtler, R.W. and Baghdadi, A. and Cota, M.},
abstractNote = {Parametric studies of silicon deposition were conducted employing the horizontal Energy Beam system. Chemical equilibrium calculations pertaining to the Energy Beam deposition conditions were performed. These calculations indicated that the reaction efficiency for hydrogen reduction of silicon tetrachloride is over 95% for any chlorosilane concentration at the Energy Beam temperature of 4300/sup 0/K. Because lower temperatures exist near the substrate surfaces, the kinetics of establishing the low temperature equilibrium will determine obtainable material efficiencies. From deposition experiments, the material efficiency was found to be strongly dependent on input chlorosilane concentrations. The highest material efficiency and growth rate obtained concurrently to date were 70% and 10 ..mu..m/min using the horizontal Energy Beam system. The Thermal Expansion Shear Separation (TESS) process for producing self supporting silicon films was further investigated.},
doi = {10.2172/5749786},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 1978},
month = {Sun Jan 01 00:00:00 EST 1978}
}
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Technical Report:
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DOI:  10.2172/5749786
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  • ; ; ; ...
    Construction of the basic apparatus for Energy Beam deposition of silicon has been completed, and the deposition experiments have begun. Deposition experiments with silane, trichlorosilane and silicon tetrachloride have all achieved relatively high growth rates together with encouraging material efficiency. For example, a deposition rate of approximately 50 ..mu../min with a material efficiency of 15.3 percent was achieved with silicon tetrachloride. The ''thermal mismatch'' approach was approved to be a good method for peeling off polycrystalline ribbon. Successful experiments were carried out on Mo and W substrates using conventional CVD from SiHCl/sub 3/ at 1500K. A preliminary thermodynamic calculation atmore » chemical equilibrium of the concentrations of atomic and molecular species shows that, in the range of the Energy Beam plasma temperature, 94 percent to 99 percent of the silicon is present as monoatomic silicon.« less

  • ; ; ; ...
    Construction of the basic apparatus for Energy Beam deposition of silicon has been completed, and the deposition experiments have begun. Deposition experiments with silane, trichlorosilane and silicon tetrachloride have all achieved relatively high growth rates together with encouraging material efficiency. For example, a deposition rate of approx.50..mu../min with a material efficiency of 15.3% was achieved with silicon tetrachloride. The thermal mismatch approach was approved to be a good method for peeling off polycrystalline ribbon. Successful experiments were carried out on Mo and W substrates using conventional CVD from SiHCl/sub 3/ at 1500K. A preliminary thermodynamic calculation at chemical equilibrium ofmore » the concentrations of atomic and molecular species shows that, in the range of the Energy Beam plasma temperature, 94% to 99% of the silicon is present as monoatomic silicon.« less

  • ;
    The purity, structural and electrical characteristics of silicon ingots obtained by various numbers of crystal pulling are reported. It is confirmed that the crystal pulling is effective for removing metallic impurities from silicon. The electrical resistivity and carrier mobility of the silicon were measured and the photoresponse was determined for gated diodes, wafers with a shallow p-n junction, epitaxy wafers with a p-n junction, in terms of the short circuit current and the open circuit voltage. The predicted cell efficiency is plotted vs the current x voltage product. (LEW)

  • Efforts were directed to the preparation and characterization of silicon films, p--n junctions, and solar cells on purified metallurgical silicon substrates. A final group of passivated epitaxial silicon mesa diodes on metallurgical silicon substrates was prepared, and their dark forward characteristics were measured and analyzed. The results have confirmed the earlier conclusion that carrier recombinations at grain boundaries can be combined with those in the space region in the two-exponential model. A high resolution apparatus for the measurement of potential barriers at grain boundaries in epitaxial silicon films on metallurgical silicon substrates was assembled. Initial measurements indicated a measurable voltagemore » drop at all grain boundaries. Large area (30 cm/sup 2/) solar cells prepared by successively depositing p- and n/sup +/-silicon films on purified p/sup +/-metallurgical silicon substrates have AM1 efficiencies of about 7.5%. The spectral response of polycrystalline silicon solar cells was measured under light bias. Preliminary work on the measurement of dopant profile in polycrystalline silicon solar cells by a combination of grooving and spreading resistance techniques was carried out.« less

  • ; ; ; ...
    The metalorganic chemical vapor deposition (MO-CVD) technique has been applied to the growth of thin films of GaAs and GaAlAs on inexpensive polycrystalline or amorphous substrate materials (primarily glasses and metals) for use in fabrication of large-area low-cost photovoltaic device structures. Trimethylgallium (TMG), arsine (AsH/sub 3/), and trimethylaluminum (TMAl) are mixed in appropriate concentrations at room temperature in the gaseous state and pyrolyzed at the substrate, which is heated in a vertical reactor chamber to temperatures of 725 to 750/sup 0/C, to produce the desired film composition and properties. The substrate materials used for experimental studies during the quarter includedmore » several grades of graphite (from two different manufacturers), commercial-grade Al alloy sheet, large-grained annealed Mo sheet, sputtered Mo films on Corning Code 0317 glass, uncoated 0317 glass, large-grained polycrystalline alumina (Coors Vistal 5), and large-grained bulk polycrystalline GaAs. Results indicted graphite to be a suitable substrate for GaAs film growth by MO-CVD, although some adherence problems were uncountered with improperly prepared graphite surfaces. No major differences were observed for GaAs growth on the various graphites; films approx. 10 ..mu..m thick exhibited apparent grain sizes (indicated by dimensions of surface features) in the 2 to 5 ..mu..m range. Annealed Mo sheet substrate having relatively large grain structure did not appear to produce correspondingly large grains in deposited polycrystalline GaAs films. Results are reported in detail. (WHK)« less