Defect levels in electrodeposited n-type CdTe thin films
Admittance spectroscopy is used to measure electron traps near the conduction band of the n-type electrodeposited CdTe thin films. Several samples of Ni-CdTe Schottky-barrier and Ni-TeO/sub 2/-CdTe devices are used in the measurement. Two donor levels with activation energies around 0.12 eV and between 0.19 and 0.26 eV are detected. In addition, there may be one or more shallow donor levels within 0.04 eV from the conduction band. Capacitance loops are observed in the capacitance-voltage measurements performed at different temperatures and bias sweep rates. The activation energies, densities, and electron-capture cross sections of the two slow electron-trap levels responding to the cyclical ramp bias are estimated. The rise and decay photocapacitance transient measurements at 295 K reveal two electron-trap levels with photoionization threshold energies of 0.8 and 1.3 eV. These two levels are suspected to correspond to the other two slow electron-trap levels estimated in the capacitance-voltage measurement and located around or above the midgap. The differences between thermal and optical ionization energies and the slow electron-capture rates of these two levels may be explained by the nonradiative, thermally activated capture processes with large lattice relaxation. Numerous defects around and below the midgap are detected by the steady-state photocapacitance measurement at 100 K. A band of seven defect levels spreading within 0.6 to 1.0 eV is observed. Large capacitance changes are recorded at 1.37, 1.41, and 1.45 eV. These three levels are speculated to be the major compensating acceptor levels.
- Research Organization:
- Department of Electrical Engineering, Columbia University, New York, New York 10027
- OSTI ID:
- 6895589
- Journal Information:
- J. Appl. Phys.; (United States), Vol. 61:6
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CADMIUM TELLURIDE SOLAR CELLS
TRAPS
CADMIUM TELLURIDES
CRYSTAL DEFECTS
ENERGY LEVELS
DEEP LEVEL TRANSIENT SPECTROSCOPY
ELECTRODEPOSITION
ELECTRONIC STRUCTURE
IMPURITIES
NICKEL
SCHOTTKY BARRIER DIODES
THIN FILMS
CADMIUM COMPOUNDS
CHALCOGENIDES
CRYSTAL STRUCTURE
DEPOSITION
DIRECT ENERGY CONVERTERS
ELECTROLYSIS
ELEMENTS
EQUIPMENT
FILMS
LYSIS
METALS
PHOTOELECTRIC CELLS
PHOTOVOLTAIC CELLS
SEMICONDUCTOR DEVICES
SEMICONDUCTOR DIODES
SOLAR CELLS
SOLAR EQUIPMENT
SPECTROSCOPY
SURFACE COATING
TELLURIDES
TELLURIUM COMPOUNDS
TRANSITION ELEMENTS
140501* - Solar Energy Conversion- Photovoltaic Conversion