Photonic circuits integrated with CMOS compatible photodetectors

This paper presents the integration of photodetectors and photonic circuits (waveguides and interferometers, coupling elements and chemo-optical transducing layer) on one silicon chip. Different materials: silicon, doped or undoped silica, SiO_xN_y, polymers, and different technologies: LPCVD, APCVD, sol-gel, spinning, micromachining have been used to realize the photonic and micromechanical components and the transducers. Also, MOS compatible processes have been used for optoelectronic circuits. The attention was focused on the matching of all the involved technologies, to allow the monolithic integration of all components, and also on the design and fabrication of special structures of photodetectors. Two types of high responsivity photodetectors, a photo-FET and a bipolar NPN phototransistor, with modified structures that allow the optical coupling to the waveguides have been designed and experimented. An original 3-D model was developed for the system: opto-FET-coupler-waveguide. A test circuit for sensor applications was experimented. All the components of the test circuits, photodetectors, waveguides, couplers, were obtained using CMOS-compatible processes. The aim of our research activity was to obtain microsensors with optical read-out.