Two-micron wavelength high speed photodiode with InGaAs/GaAsSb type-II multiple quantum wells absorber

Current optical communication system operating at 1.55 {\mu}m wavelength band may not be able to continually satisfy the growing demand on the data capacity within the next few years. Opening a new spectral window at around 2 {\mu}m wavelength with recently developed hollow-core photonic band gap fiber and thulium-doped fiber amplifier is a promising solution to increase the transmission capacity due to the low loss and wide bandwidth properties of these components at this wavelength. However, as a key component, the already demonstrated high speed photodetectors at 2 {\mu}m wavelength are still not comparable with those at 1.55 {\mu}m wavelength band, which chokes the feasibility of the new spectral window. In this work, we, for the first time, demonstrated a high speed uni-traveling carrier photodiode for 2 {\mu}m applications with InGaAs/GaAsSb type-II multiple quantum wells as the absorption region, which is lattice matched to InP. The device shows a 3dB bandwidth of 25 GHz at -3 V bias voltage and is, to the best of our knowledge, the fastest photodiodes among all group III-V and group IV photodetectors working in 2 {\mu}m wavelength range.