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/cm(2) at -1 V bias has been measured at room temperature; when heated to 85 degrees C, 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 pm diameter Ge detectors. (C) 2008 Elsevier B.V. All rights reserved.