A study is presented on silicon oxynitride material for waveguides and germanium-silicon alloys for p-in diodes. The materials are manufactured at low, CMOS-backend compatible temperatures, targeting the integration of optical functions on top of CMOS chips. Low-temperature germanium-silicon deposition, crystallization and doping are studied for integrated photo detection up to similar to 1500 nm wavelength. An investigation of the process window for laser crystallization is presented aiming toward the localization control of crystal boundaries and the achievement of crystals larger than 2 mu m. Further, an inductively-coupled-plasma chemical vapor deposition process is presented for silicon oxynitride manufacturing at 150 degrees C wafer temperature, yielding low-loss material in a wide optical spectral range. Integration schemes for an optical plane on top of CMOS using these materials are discussed. (C) 2014 Elsevier Ltd. All rights reserved.