Near-infrared photodetectors based on polycrystalline Ge evaporated on Si < 100 > substrates

We report the fabrication of efficient near-infrared photodetectors based o n polycrystalline Ge films on Si[100]. In view of integration with Si elect ronics, metal-semiconductor-metal photodiodes have been realized, for the f irst time to the best of our knowledge, by low-temperature evaporation. The experiments performed on non-optimized devices indicate a substantial sens itivity at both 1.32 and 1.55 mu m, with a responsivity as high as 16 mA W- 1 at 1.32 mu m with 0.2 V bias, and a time response of about 4 ns.