Thermally tunable Ge waveguide photodetector with a wide operating wavelength range.

In this work, we present the design and fabrication of a germanium waveguide p-i-n photodetector with on-chip thermal tuning. Theoretical simulations demonstrate that applying a 3 V heat-tuned voltage can raise the temperature of the germanium absorber layer to 379 K and extend the detection wavelength range to the L-band. The experimental results confirm that the device can operate effectively from 1525 to 1625 nm. The responsivity can reach up to 0.72 A/W at 1625 nm. The frequency response measurement reveals a 3 dB bandwidth () higher than 40 GHz at -3. Further increasing the heat-tuned voltage cannot improve the absorption in the L-band significantly but does lead to higher dark current.