High performance waveguide-coupled germanium p-i-n photodetector on doped silicon

Waveguide-coupled germanium (Ge) p-i-n photodetectors (PDs) have attracted much attention and have been investigated widely due to their high performance and enable on-chip integration. Conventional waveguide-coupled Ge PDs requires metal contact on Ge as well as doping in Ge to form the p-i-n junction. However, in these devices, the light absorption of metal contacts on Ge leads to a sharp decrease in responsivity. In addition, in the standard CMOS foundries, the technology of forming metal contact with Ge is immature. In this paper, we report on the design, fabrication, and experimental demonstration of an integrated lateral waveguide p-i-n photodetector (PD). We experimentally obtained at a reverse voltage of 3V a dark current of 11 nA, a responsivity higher than 0.73 A/W at 1550 nm wavelength, and a -3 dB opto-electrical cut-off frequency over 66 GHz. The combined benefits of decreased process complexity and high-performance device operation pave the way towards attractive integration strategies to deploy costeffective photonic transceivers on silicon-on-insulator substrates.