Extended near infrared photo-response influenced by host matrix change in Ge nanoparticle-based films

Ge nanoparticles in SiO 2 or Si 3 N 4 on Si pieces at 500 °C were fabricated by sputtering from Ge, SiO 2 or Si 3 N 4 targets. Transmission electron microscopy, current - voltage and spectral-photocurrent characteristics were done to determine the structure and photo-electrical behaviour. Depending on the temperature, the current under illumination, for both films, are comparable and increase with more than 5 orders of magnitude over the dark one. Even if obtaining parameters are similar, photo-current spectra in photovoltaic regime show for Ge:SiO 2 a cut-off wavelength of 1377 nm and an extended sensitivity threshold in near infrared of 1560 nm for Ge:Si 3 N 4 .films.