Dresden 2014 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 45: Optical properties II

HL 45.2: Talk

Tuesday, April 1, 2014, 11:30–11:45, POT 006

Optical characterization of germanium nanostructures — •Anna-Sophie Pawlik, Jan Beyer, Peter Seidel, Maximilian Geyer, and Johannes Heitmann — Technische Universität Bergakademie Freiberg, Institut für Angewandte Physik

The optical properties of Germanium nanostructures (Ge ns) embedded in a ZrO₂ Matrix were investigated. The samples have been prepared by a co-sputtering-process, at which superlattices consisting of ZrO₂ and Ge/ZrO₂ mixed layers have been deposited on a silicon substrate with and without a silicon nitride (SiN_x) layer. SiN_x was used to prevent a reaction of the ZrO₂ with the native silicon oxide. During rapid thermal processing the formation of Ge ns takes place through a decomposition of the mixed layer. Photoluminescence (PL) measurements have been carried out at temperatures variing from 13 to 300 K. For the visible spectral region, two PL peaks were observed at room temperature, centred at around 2.2 eV and 2.9 eV. These peaks do not correlate with the crystallinity and concentration of the Ge ns. It has been concluded, that these peaks are defect related. Only for samples with a SiN_x layer underneath the superlattices, PL in the infrared wavelength at around 0.83 eV could be observed at low temperatures. Temperature dependent measurements showed a redshift of the PL peak position and a decreasing intensity with increasing temperature. Further investigations indicate that this PL Signal is attributed to the band to band recombination in the Ge ns. This assumption is confirmed by Raman measurements, which show a peak for crystalline Ge at around 300 cm⁻¹ for the samples which show PL in the IR region.