Dresden 2006 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 9: Poster I

HL 9.52: Poster

Montag, 27. März 2006, 15:15–17:45, P3

Charge trapping at Si(100)-ZrO₂ interfaces studied by second-harmonic generation — •Bastian Manschwetus, Armin Rumpel, Peter Iskra, Gerhard Lilienkamp, and Winfried Daum — Institut für Physik und Physikalische Technologien, TU Clausthal, Leibnizstrasse 4, D-38678 Clausthal-Zellerfeld

Thin ZrO₂ layers deposited on Si(100) substrates by a sol-gel technique have been studied by second-harmonic generation (SHG) spectroscopy using femtosecond laser pulses. SHG spectra in the two-photon energy range between 3.1 eV and 4.2 eV are dominated by interband transitions at the main bulk critical-points of silicon (E₁ at 3.3 eV and E₂ at 4.4 eV) and by a specific interface transition at 3.6 eV. Fixed-frequency measurements at 730 nm and 700 nm laser wavelength (1.70 eV and 1.77 eV, respectively) show a pronounced time dependence of the SHG signal. This time dependence on the scale of seconds to several minutes describable by two exponentials varies as the intensity of the exciting laser beam is increased. In analogy to previous results of other groups obtained for Si-SiO₂ systems we relate the time dependence of the SHG signal to a quasi-static electric field giving rise to electric-field-induced SHG at the silicon side of the interface. This field is caused by multi-photon excitation of electrons and holes in the ZrO₂ layer and subsequent trapping of a part of these charges in defects of the ZrO₂ layer. At lower laser intensities electron excitation into the ZrO₂ conduction band is the dominant mechanism as it requires only two-photon excitation. Hole excitation into the ZrO₂ valence band requires three-photon excitation and becomes important only at higher intensities.