Low-Capacitance Integrated Silicon Finger Photodetector

Results of a low capacitance design for integrated silicon photodiodes are presented. The diodes use n ⁺ -doped finger cathodes as well as p ⁺ -fingers. With this design it is possible to lower the capacitance compared to homogenous photodiodes (vertical PIN photodiode structure). Low capacitances are reached even at low bias voltages of around 2 V. The diodes reach a responsivity of R=0.24A/W (0.45A/W) at a wavelength of 410 nm (660 nm). The diode design aims at applications where maximum sensitivity, i.e. lowest noise, and therefore low photodiode capacitance is needed. The photodiodes were realized in a 0.6mum BiCMOS process