Performance of Ge-on-Si p-i-n Photodetectors for Standard Receiver Modules

Ge on Si p-i-n photodetectors with areas which are compatible with commercially available receivers have been fabricated and tested. A dark current density of 6 mA/cm² at -1-V bias has been measured at room temperature; when heated to 85 degC, the measured dark current increases by a factor of nine. A responsivity of 0.59 A/W at 850 nm has been measured from these Ge detectors, which matches or exceeds commercially available GaAs devices. We have measured bandwidths approaching 9 GHz at -2-V bias from 50-mum diameter Ge detectors, and have observed eye diagrams comparable to those obtained from GaAs-based receivers at 4.25 Gb/s