Back-side-illuminated high-speed Ge photodetector fabricated on Si substrate using thin SiGe buffer layers

We report photodiodes fabricated on Ge grown on Si substrate. The Ge growth was preceded by two SixGe1-x buffer layers. Dark current as low as 1.07 muA was achieved at 10 V reverse bias for 24 mum-diam mesa devices. At 1.3 mum wavelength, the responsivity was 0.37 A/W at 0 V and 0.57 A/W when above TV reverse bias. The 3 dB bandwidth was 8.1 GHz at a reverse bias of 10 V. (C) 2004 American Institute of Physics.