Ge-on-Si pin-photodiodes for vertical and in-plane detection of 1300 to 1580 nm light

Ge-on-Si pin-photodiodes for vertical and in-plane detection are presented. The devices are grown on an 31 nm ultrathin, strain relaxed buffer (SRB) layer. The vertical photodiode exhibits a zero-bias responsivity of 117 mA/W and a bandwidth of 1.5 GHz at a wavelength of 1298 nm. In comparison, the detector for in-plane detection has a zero-bias responsivity of 70 mA/W and a bandwidth of 4.4 GHz. For a bias voltage of -2 V a bandwidth of 6.2 GHz has been measured. At 1580 nm the photo responsivity of the lateral photodiode is higher (26 mA/W) than of the vertical photodiode (19 mA/W). The dislocation density probably may limit the bandwidth.