Low-Dark Current 1.55 Micrometer InAs Quantum Dash Waveguide Photodiodes

We demonstrate the first C-band InAs quantum dash (Qdash) waveguide photodiodes (PDs) with a record-low dark current of 5 pA, a responsivity of 0.26 A/W at 1.55 μm, and open eye diagrams up to 10 Gb/s. The dark current density of 3.3×10-7 A/cm2 is around five orders of magnitude lower than the state-of-art Ge PDs, and two orders of magnitude lower than commercial InGaAs PDs. The Qdash-based PDs leverage the same epitaxial layers and processing steps as Qdash lasers and can thus be integrated with laser sources for power monitors or amplifiers for pre-amplified receivers, manifesting themselves as a promising alternative to their InGaAs and Ge counterparts in low-power optical communication links.