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HELIOS results: 40 GBit/s germanium photodetector

Within the frame of HELIOS, the University of Paris-Sud (UPS-IEF) demonstrated a 40 GBit/s germanium photodetector integrated in silicon-on-insulator waveguide

The results have been published by L. Vivien et al. Optics Express 17 (8), 6252-6257 (2009) and at Group IV Photonics, San Francisco, USA, 9-11 September 2009

Integrated photodetector is one of the main building blocks for silicon photonic applications for either monitoring or high speed detection. For this purpose, germanium (Ge) is exploited thanks to its strong absorption coefficient. In the frame work of the European project HELIOS, a vertical pin Ge photodetector integrated in submicron SOI rib waveguide has been developed. As butt coupling configuration is considered, the detector length to totally absorb incident light at the wavelength of 1.55 µm, is reduced down to 15 µm (figure 1a). Such a waveguide detector, reported in figure 1b uses a process fully compatible with CMOS technology. The responsivity as high as 1 A/W under -4V and a dark current density as low as 60 mA/cm² has been obtained. An open eye diagram at 40 Gb/s under -4V is presented in figure 1c

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Figure 1: (a) Schematic view of vertical pin Ge-on-Si diode integrated in rib waveguide. (b) Top view of waveguide Ge photodetector. (c) Open eye diagram at 40Gbit/s.