High-purity silicon crystal growth investigations. Final technical progress report, September 1, 1984-March 31, 1986
This report explores a number of crystal growth effects that affect minority-carrier lifetime. The effects of impurity redistribution under the combined actions of segregation and evaporation during crystal growth were investigated mathematically. Metallic impurity reduction by evaporation is substantial during float zoning, and most metallic impurity concentrations should decrease by two to four orders of magnitude after one vacuum float-zoning pass. Two float-zoning passes in vacuum reduce most metallic impurity concentrations by more than four orders of magnitude, and three passes by more than six orders of magnitude. Minority-carrier lifetime was determined as a function of dopant density for four p-type dopants. Boron and gallium may be more favorable dopants than indium or aluminum for obtaining high lifetimes concomitant with heavy doping levels. The feasibility of achieving lifetimes greater than 100 ..mu..s at doping levels as high as 2 x 10/sup 17/ atoms/cm/sup 3/ (0.17 ohm-cm) was shown. Minority-carrier lifetime decreased as the crystal cooling rate increased in dislocation-free crystals. The dislocations, even at relatively low concentrations (2 x 10/sup 4//cm/sup 2/), drastically reduce minority-carrier lifetime. A variety of defects in dislocation-free FZ crystals and dislocated ribbons were investigated by x-ray topography.
- Research Organization:
- Solar Energy Research Inst., Golden, CO (USA)
- DOE Contract Number:
- AC02-83CH10093
- OSTI ID:
- 5294268
- Report Number(s):
- SERI/PR-212-2926; ON: DE86010738
- Resource Relation:
- Other Information: Portions of this document are illegible in microfiche products. Original copy available until stock is exhausted
- Country of Publication:
- United States
- Language:
- English
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36 MATERIALS SCIENCE
SILICON
CRYSTAL GROWTH
CARRIER LIFETIME
CRYSTAL DEFECTS
CRYSTAL DOPING
SILICON SOLAR CELLS
VACUUM EVAPORATION
ZONE MELTING
CRYSTAL STRUCTURE
DIRECT ENERGY CONVERTERS
ELEMENTS
EQUIPMENT
EVAPORATION
LIFETIME
MELTING
PHASE TRANSFORMATIONS
PHOTOELECTRIC CELLS
PHOTOVOLTAIC CELLS
SEMIMETALS
SOLAR CELLS
SOLAR EQUIPMENT
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