The electronic structure of single-crystal
(In)GaAs deposited with tri-methylaluminum (TMA) and water via atomic layer
deposition (ALD) is presented with high-resolution synchrotron radiation
core-level photoemission and capacitance-voltage (CV) characteristics. The
interaction of the precursor atoms with (In)GaAs is confined at the topmost
surface layer. The Ga-vacant site on the GaAs(111)A-2 × 2 surface is filled
with Al, thereby effectively passivating the As dangling bonds. The As-As
dimers on the GaAs(001)-2 × 4 surface are entirely passivated by one cycle of
TMA and water. The presumed layerwise deposition fails to happen in GaAs(001)-4
× 6. In In0.20Ga0.80As(001)-2 × 4, the edge row As atoms are partially bonded
with the Al, and one released methyl then bonds with the In. It is suggested
that the unpassivated surface and subsurface atoms cause large frequency
dispersions in CV characteristics under the gate bias. We also found that the
(In)GaAs surface is immune to water in ALD. However, the momentary exposure of
it to air (less than one minute) introduces significant signals of native
oxides. This indicates the necessity of in situ works of high
κ/(In)GaAs-related experiments in order to know the precise interfacial atomic
bonding and thus know the electronic characteristics. The electric CV
measurements of the ALD-Al2O3 on these (In)GaAs surfaces are correlated with
their electronic properties.
Source:IOPscience
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