Trapped charge densities in Al{sub 2}O{sub 3}-based silicon surface passivation layers

In Al{sub 2}O{sub 3}-based passivation layers, the formation of fixed charges and trap sites can be strongly influenced by small modifications in the stack layout. Fixed and trapped charge densities are characterized with capacitance voltage profiling and trap spectroscopy by charge injection and se...

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Bibliographic Details
Published in:Journal of applied physics 2016-06, Vol.119 (21)
Main Authors: Jordan, Paul M., Simon, Daniel K., Dirnstorfer, Ingo, Mikolajick, Thomas, Chair of Nanoelectronic Materials, TU Dresden, D-01062 Dresden
Format: Article
Language:English
Subjects:
ALUMINIUM OXIDES
CAPACITANCE
CARRIER LIFETIME
CHARGE DENSITY
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
COMPARATIVE EVALUATIONS
CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
HAFNIUM OXIDES
LAYERS
PASSIVATION
SILICA
SILICON
SILICON OXIDES
SOLAR CELLS
SPECTROSCOPY
STACKS
STRESSES
SURFACES
THICKNESS
TRAPPING
TRAPS
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Summary:In Al{sub 2}O{sub 3}-based passivation layers, the formation of fixed charges and trap sites can be strongly influenced by small modifications in the stack layout. Fixed and trapped charge densities are characterized with capacitance voltage profiling and trap spectroscopy by charge injection and sensing, respectively. Al{sub 2}O{sub 3} layers are grown by atomic layer deposition with very thin (∼1 nm) SiO{sub 2} or HfO{sub 2} interlayers or interface layers. In SiO{sub 2}/Al{sub 2}O{sub 3} and HfO{sub 2}/Al{sub 2}O{sub 3} stacks, both fixed charges and trap sites are reduced by at least a factor of 5 compared with the value measured in pure Al{sub 2}O{sub 3}. In Al{sub 2}O{sub 3}/SiO{sub 2}/Al{sub 2}O{sub 3} or Al{sub 2}O{sub 3}/HfO{sub 2}/Al{sub 2}O{sub 3} stacks, very high total charge densities of up to 9 × 10{sup 12} cm{sup −2} are achieved. These charge densities are described as functions of electrical stress voltage, time, and the Al{sub 2}O{sub 3} layer thickness between silicon and the HfO{sub 2} or the SiO{sub 2} interlayer. Despite the strong variation of trap sites, all stacks reach very good effective carrier lifetimes of up to 8 and 20 ms on p- and n-type silicon substrates, respectively. Controlling the trap sites in Al{sub 2}O{sub 3} layers opens the possibility to engineer the field-effect passivation in the solar cells.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.4953141