100 Gbps PAM4 ultra-thin photodetectors integrated on SOI platform by micro transfer printing

The integration of compact high-bandwidth III-V active devices in a scalable manner is highly significant for Silicon-on-insulator (SOI) photonic integrated circuits. To address this, we demonstrate the integration of pre-fabricated 21 × 57 µm² InGaAs photodetector (PD) coupons with a thickness of 675 nm to a 500 nm SOI platform using a direct bonding micro-transfer printing process. The common devices are coupled to the Si waveguides via butt, grating and evanescent coupling schemes with responsivities of 0.13, 0.3 and 0.6 A/W respectively, in line with simulations. The thin device facilitates simplified high-speed connections without the need for an interlayer dielectric. A back-to-back data communication rate of 50 Gb/s is achieved with on-off keying and with post processing of four-level pulse-amplitude modulation (PAM4) 100 Gb/s is realized. Potentially, around 1 million devices per 75 mm InP wafer can be attained. The integration of compact PDs exhibited in this work can be extended to modulators and lasers in the future.