| Schottky barrier sub-bandgap photodetectors have been produced by depositing thin (∼10 run) Ni metal layers over silicon-on-insulator (SOI) rib waveguides defined by the Local Oxidation of Silicon (LOCOS) technique. Absolute responsivities of 0.47 mA/W and 0.18 mA/W were obtained for a 500mum long photodiode with a rib width of 3 mum at wavelengths of 1310 run and 1550 run, respectively. Allowing for the optical insertion loss for light entering the waveguide, the adjusted responsivity is 4.7 mA/W and 1.8 mA/W at 1310 nm and 1550 run wavelength, respectively. The reverse leakage dark current is just 0.3 nA at 1 V reverse bias. The responsivity is comparable to that obtained in SOI waveguide photodetectors fabricated using the ion implant damage technique, but the reverse leakage current should be far lower. These devices could find application in optical telecommunication and optical sensing applications. |
