Germanium Photodiodes with 3-dB Bandwidths >110 GHz and L-Band Responsivity of >0.7 A/W

We present germanium p-i-n photodiodes with opto-electrical 3-dB bandwidths >110 GHz while exhibiting high internal responsivity >0.7 AW ^-1 at 1620 nm wavelength. Compared to our previous work, this is an improvement of >35 % in internal responsivity without sacrificing the photo detectors bandwidths. This was achieved by the introduction of a local reduction of the silicon waveguide thickness right below the germanium body, which improves optical coupling (from the silicon waveguide into the germanium region) and confinement. In this work we study three photodiode device variants in which germanium is laterally sandwiched between complementary in-situ doped Si regions. This approach enables the side-by side realization of germanium p-i-n photodiodes with different widths, featuring different combinations of OE bandwidths and responsivities. We further investigate on the optical-power handling capabilities of these photodiodes by means of responsivity and bandwidth.