Vertical MSM photodiodes in silicon based on epitaxial Si/CoSi 2/Si

Abstract

We present performance data of new ultrafast metal–semiconductor–metal photodiodes, fabricated by Si/CoSi 2 layer growth on (100) and (111) silicon. The design of these vertical diodes avoids expensive direct electron beam writing. If a mode-locked Ti:sapphire laser of 800 nm wavelength and 0.15 ps pulse length is used for excitation from the top, the diodes deliver a fast electrical pulse response of 7 ps FWHM at 50 K for Si(100) and of 6.5 ps for Si(111), also at room temperature, which is in full agreement with the design parameters. Quantum efficiencies up to 15% seem to be feasible with an integrated optical waveguide which couples the light from the side into the photodiode.