Evidence of a thermally stimulated charge transfer mechanism and interface defect formation in metal-oxide-semiconductor structures with germanium nanocrystals


Evidence of a thermally stimulated charge transfer mechanism and interface defect formation in metal-oxide-semiconductor structures with germanium nanocrystals

Beyer, R.; von Borany, J.

The trapping of charge carriers and the mechanism of the charge transfer were examined in metal-oxide-semiconductor structures with germanium nanocrystals embedded in a 20 nm silicondioxide layer. The nanoclusters were generated by ion beam synthesis. Capacitance-voltage (C-V) measurements exhibit a hysteresis loop due to the charge trapping and detrapping. Effective oxide trap densities were derived and could be related to the nanoclusters. A strong temperature dependence of the C-V loop indicates, that a thermally stimulated process is involved in the charge transfer between the clusters and the interface, thus ruling out direct tunneling. The application of deep level transient spectroscopy revealed a large amount of interface states in the Ge implanted samples, including a distinct trap state at 0.32 eV above the valence band edge with a concentration up to 2e13 /(cm²eV), which is much likely involved in the emission of carriers from cluster related states in a two stage process.

Keywords: Ion beam synthesis; Ge nanocrystals; CV characteristics

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Publ.-Id: 12312