Low-temperature germanium thin films on silicon

V. Sorianello, L. Colace, N. Armani, F. Rossi, C. Ferrari, L. Lazzarini and G. Assanto

Opt. Mater. Express 1 (5), 856-865 (2011)


We discuss thermal evaporation of Germanium thin films as a suitable route to realizing near-infrared detectors integrated on a Silicon platform. We study the structural properties of samples grown at various substrate temperatures by X-ray diffraction and transmission electron microscopy, showing that Ge thin films are amorphous when deposited below 225C, mono-crystalline between 225 and 400C, poly-crystalline above 450C. We further investigate their optical and electrical properties using differential optical absorption spectroscopy, Hall and photocurrent measurements. Finally, with the evaporated Ge thin films we demonstrate near-infrared photodiodes with low dark current density and good responsivity at 1.55 Mum.