Investigation of the bandwidth of geiger-mode avalanche photodiodes

Considerable interest currently exists in the use of plastic optical fibre (POF) for short distances data communications. Attenuation in POF is reduced at 650 nm compared to longer wavelength light and hence silicon based photoreceivers are ideal candidates for use with POF. The difficulty with the development of a CMOS photoreceiver, however, is the realisation of a high speed CMOS photodiode. This paper presents CMOS compatible, shallow junction Geiger-mode avalanche photodiodes (GMAPs) and investigates their bandwidth at 650 nm. Various sized GMAPs (500 μm and 250 μm diameter GMAPs with 20 μm cathode-anode overlaps and 20 μm diameter GMAPs with 3 μm, 4 μm and 5 μm overlaps) were mounted on PCBs. The anodes and cathodes were wirebonded to ground and 50 Ω transmission lines respectively. Impulse response measurements were made for each diode over a range of bias voltages, using a 650 nm picosecond pulsed laser diode. The bandwidths of each diode were calculated from the measured impulse responses and plots of bandwidth versus reverse bias were made. The results indicate very high speed operation is possible (> 1 GHz (20 μm diameter diode)), even for large detectors (> 250 MHz (500 μm diameter diode)).