InP-based high-speed monolithic PIN photodetector integrated with an MQW semiconductor optical amplifier

Abstract

We demonstrate an InP-based high-speed monolithic PIN photodetector (PD) integrated with a multi-quantum well semiconductor optical amplifier (SOA). A butt-joint scheme is adopted to connect the SOA and evanescent wave PD. The chip allows for a separate design for the SOA and the PD, and needs only two metal-organic chemical vapor deposition growth steps, which promises high yield and reduced manufacturing cost. The fabricated PD shows a low dark current of 300 pA at −3V. The optical gain bandwidth of the SOA is 50 nm, covering the whole c-band. The gain ripple of the SOA is 0.5 dB, indicating that the internal parasitic reflectivity is negligible. For an integrated chip with a 500 μm SOA, the on-chip gain and total chip responsivity at 1545 nm can reach 12.8 dB and 7.8 A W−1, respectively. The insertion loss of the butt-joint interface is estimated to be 1.05 dB/interface. The small signal 3 dB bandwidth at −5V of the integrated chip reaches 20 GHz, showing no deterioration compared to a discrete PD.