Research on the structural and electronic properties of defects in amorphous silicon

Technical Report · Fri Jun 01 00:00:00 EDT 1990

OSTI ID:6854280

Street, R A; Boyce, J B; Jackson, W B; Johnson, N; Ready, S E; Thompson, R; Tsal, C C; Walker, J; Winer, K ^[1]

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1. Xerox Palo Alto Research Center, CA (USA)

The objective of this research program is to obtain a comprehensive understanding of the structure and electronic properties of a-Si:H. The main emphasis is on the phenomena of metastability and thermal equilibrium, in which the density of electronic states depend on the electronic and thermal history of the material. Metastability effects are a problem with solar cells and with other electronic devices. Our studies provide an understanding of the complex interaction between the electronic states and the atomic structure which cause these effects. One of the main materials problems of amorphous silicon technology is the phenomenon of metastability, in which the electronic properties depend on the thermal and electrical history of the sample. A key observation is that the defects are in thermal equilibrium with the disordered structure. The experiments confirm that defect equilibration occurs over a range of temperatures and sample deposition conditions. The relaxation time depends on the growth conditions, and the thermal defects are shown to anneal more slowly than optically induced defects. The temperature dependence of the thermodynamic equilibrium defect density is calculated, based on a hydrogen mediated weak-bond/dangling-bond conversion model. The distribution of defect formation energies is introduced by associating a different density of valence band tail states with each formation energy. A detailed analysis of the connection between hydrogen diffusion and the relaxation kinetics finds excellent agreement with the data. 17 refs., 24 figs.

• Research Organization: Solar Energy Research Inst., Golden, CO (USA); Xerox Palo Alto Research Center, CA (USA)
• Sponsoring Organization: DOE/CE
• DOE Contract Number: AC02-83CH10093
• OSTI ID: 6854280
• Report Number(s): SERI/TP-211-3830; ON: DE90000342
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
36 MATERIALS SCIENCE
SILICON
AMORPHOUS STATE
SOLAR CELLS
METASTABLE STATES
ANNEALING
CHEMICAL BONDS
CHEMICAL REACTIONS
DEFECTS
DENSITY
DIFFUSION
DOPED MATERIALS
ELECTRICAL PROPERTIES
ENERGY LEVELS
INTERACTIONS
MEASURING METHODS
MICROSTRUCTURE
PROGRESS REPORT
RESEARCH PROGRAMS
SEMICONDUCTOR MATERIALS
SPIN
TEMPERATURE EFFECTS
THERMAL EQUILIBRIUM
ANGULAR MOMENTUM
CRYSTAL STRUCTURE
DIRECT ENERGY CONVERTERS
DOCUMENT TYPES
ELEMENTS
EQUILIBRIUM
EQUIPMENT
EXCITED STATES
HEAT TREATMENTS
MATERIALS
PARTICLE PROPERTIES
PHOTOELECTRIC CELLS
PHOTOVOLTAIC CELLS
PHYSICAL PROPERTIES
SEMIMETALS
SOLAR EQUIPMENT
140501* - Solar Energy Conversion- Photovoltaic Conversion
360602 - Other Materials- Structure & Phase Studies
360603 - Materials- Properties