Near-infrared waveguide photodetectors based on polycrystalline Ge on silicon-on-insulator substrates

Polycrystalline germanium thermally evaporated on silicon has been demonstrated as a feasible way to the integration of fast near-infrared photodetectors and functional devices on silicon. However, the use of such devices is currently limited to applications which do not depend critically on responsivity. Several attempts are under investigation to overcome the problem: one of the most promising is the integration of a poly-Ge photodetector with a waveguiding structure. This approach allows the distributed absorption of the incoming light in the thin sensitive layer of the poly-Ge/Si heterojunction, thus increasing the effective absorption length and efficiency.