Electron and hole transport in a-italic-Si/sub 1-//sub x-italic/Ge/sub x-italic/:H alloys
Amorphous Si/sub 1-//sub x-italic/Ge/sub x-italic/:H films and p-italic-i-italic-n-italic diodes were fabricated by decomposition of SiH/sub 4//GeH/sub 4/ mixtures in a triode glow-discharge reactor. The photoconductivity under AM1 illumination in these alloys was constant over a range of band gaps between 1.8 (x-italic = 0) and 1.5 eV (x-italic = 0.25), while the solar cell conversion efficiency decreased at the same time from 8.6% to 4.3%. This can be explained by a reduction in the ..mu..tau product for holes with rising x-italic in undoped samples as revealed by time-of-flight experiments. In contrast to ..mu..tau, the hole drift mobility ..mu../sub D-italic//sub ,//sub h-italic/ remains constant. The opposite behavior is observed for electrons, whose drift mobility ..mu../sub D-italic//sub ,//sub e-italic/ decreases as the mobility activation energy E-italic/sub A-italic/ increases. The relation between E-italic/sub A-italic/ and ..mu../sub D-italic//sub ,//sub e-italic/ for variable x-italic is suggestive of the Meyer--Neldel rule for the conductivity. In conjunction with space-charge-limited current and sub-band-gap absorption data we conclude that only the conduction-band tail is widened by the incorporation of Ge while the valence-band tail remains unaffected. The transport data for x-italic>0 can no longer be explained by a purely exponential conduction-band tail. The rising density of midgap states shows an increasing capture cross section for holes and a decreasing one for electrons.
- Research Organization:
- Siemens Research Laboratories, Otto-Hahn-Ring 6, 8000 Muenchen 83, Federal Republic of Germany
- OSTI ID:
- 5398497
- Journal Information:
- J. Appl. Phys.; (United States), Vol. 60:6
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
GERMANIUM ALLOYS
CHARGED-PARTICLE TRANSPORT
PHOTOCONDUCTIVITY
SEMICONDUCTOR DIODES
FABRICATION
SILICON ALLOYS
SOLAR CELLS
EFFICIENCY
AMORPHOUS STATE
ELECTRON MOBILITY
EXPERIMENTAL DATA
GERMANIUM SILICIDES
HOLE MOBILITY
ALLOYS
DATA
DIRECT ENERGY CONVERTERS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
EQUIPMENT
GERMANIUM COMPOUNDS
INFORMATION
MOBILITY
NUMERICAL DATA
PARTICLE MOBILITY
PHOTOELECTRIC CELLS
PHOTOVOLTAIC CELLS
PHYSICAL PROPERTIES
RADIATION TRANSPORT
SEMICONDUCTOR DEVICES
SILICIDES
SILICON COMPOUNDS
SOLAR EQUIPMENT
140501* - Solar Energy Conversion- Photovoltaic Conversion
360603 - Materials- Properties