Chemical vapor deposition of thin-film polycrystalline Si for low-cost solar cells. Second quarterly technical progress report for period November 3, 1979 through February 1, 1980
A research program is in progress for the development of thin-film polycrystalline Si solar cells on low-cost substrate material. The results of the second quarter of work are described. The main emphasis has been on investigation of the transport properties of p-type polycrystalline Si films (formed by SiH/sub 4/ pyrolysis in H/sub 2/) as functions of grain size and acceptor doping concentration. The study has involved preparation of sets of polycrystalline films grown simultaneously on polycrystalline high-purity alumina substrates in a range of average grain sizes (approx. 1 ..mu..m to approx. 125 ..mu..m) and with a range of impurity doping concentrations from approx. 10/sup 15/ to >10/sup 20/ cm/sup -3/, primarily at approx. 985/sup 0/C. The doping concentrations are deduced from measurements of free carrier concentrations in simultaneously grown and identically doped single-crystal films on single-crystal alumina (i.e., sapphire) substrates. In addition to room-temperature measurements of resistivity and carrier concentration (and thus Hall mobility) made routinely on all of the films, selected sets of films have been characterized in detail by measurements as a function of sample temperature in the range 77 to 420/sup 0/K. The results to date confirm many of the features of the grain-boundary trapping model for conduction in polycrystalline Si, including the existence of a mobility minimum for an impurity doping concentration the magnitude of which varies with the average grain size in the film, the existence of barriers in the grain boundaries with heights that also are a function of doping concentration, and a strong dependence of free carrier concentration on the impurity doping concentration for values below that for which the mobility is a minimum. There are some pronounced differences in detail between the experimental results and the model, however, including that for the apparent area density of traps in the grain boundaries.
- Research Organization:
- Rockwell International Corp., Anaheim, CA (USA). Electronic Devices Div.
- DOE Contract Number:
- AC03-79ET23045
- OSTI ID:
- 5198391
- Report Number(s):
- DOE/ET/23045-2
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
SILICON
CHEMICAL VAPOR DEPOSITION
CRYSTAL DOPING
SILICON SOLAR CELLS
FABRICATION
GRAIN BOUNDARIES
CARRIER DENSITY
CARRIER MOBILITY
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
EPITAXY
EXPERIMENTAL DATA
FILMS
GRAIN SIZE
GRAPHS
HOLES
POLYCRYSTALS
SUBSTRATES
TEMPERATURE DEPENDENCE
TRAPS
CHEMICAL COATING
CRYSTAL STRUCTURE
CRYSTALS
DATA
DATA FORMS
DEPOSITION
DIRECT ENERGY CONVERTERS
ELEMENTS
EQUIPMENT
INFORMATION
MICROSTRUCTURE
MOBILITY
NUMERICAL DATA
PHOTOELECTRIC CELLS
PHOTOVOLTAIC CELLS
PHYSICAL PROPERTIES
SEMIMETALS
SIZE
SOLAR CELLS
SOLAR EQUIPMENT
SURFACE COATING
140501* - Solar Energy Conversion- Photovoltaic Conversion
360601 - Other Materials- Preparation & Manufacture