The adoption of all-silicon-based optical receivers has been actively pursued as an attractive alternative to III-V technology for low cost optical communication applications. In particular, germanium-on-silicon (Ge-on-Si) has been extensively explored for near-infrared photo-detection application due to its integration compatibility with existing CMOS technology and large absorption coefficient. By employing the selective epitaxy growth of Ge on silicon substrate, p-i-n Ge photodetectors have been demonstrated with good responsivity and quantum efficiency for optical absorption at wavelength λ of 850 nm.

Recently, IME researchers have demonstrated surface illuminated p-i-n Ge photodetectors fabricated on silicon-on-insulator substrate for even longer wavelength (λ= 1550 nm) photo-detection applications. Excellent device performance were achieved in these Ge-on-SOI photodetectors, leading to a low dark current of ~100 nA, responsivity of ~200 mA/W and a 3dΒ bandwidth of ~10 GHz for a given applied bias VΑ of 1.0 V. Further performance enhancement would be expected when such devices are integrated with a Si rib waveguide structure, making these high performance Ge-on-SOI photodetectors attractive for both C- and L-band photo-detection applications.