A New Paradigm in High-Speed and High-Efficiency Silicon Photodiodes for Communication—Part II: Device and VLSI Integration Challenges for Low-Dimensional Structures

The ability to monolithically integrate high-speed photodetectors (PDs) with silicon (Si) can contribute to drastic reduction in cost. Such PDs are envisioned to be integral parts of high-speed optical interconnects in the future intrachip, chip-to-chip, board-to-board, rack-to-rack, and intra-/interdata center links. Si-based PDs are of special interest since they present the potential for monolithic integration with CMOS and BiCMOS very-large-scale integration and ultralarge-scale integration electronics. In the second part of this review, we present the efforts pursued by the researchers in engineering and integrating Si, SiGe alloys, and Ge PDs to CMOS and BiCMOS electronics and compare the performance of recently demonstrated CMOS-compatible ultrafast surface-illuminated Si PD with absorption-enhancing low-dimensional structures. We discuss the advantages and challenges of device design with micro-/nanostructures, and finally, we conclude with the future directions that low-dimensional structures can offer to potentially cause a paradigm shift in high-performance PD design for various applications such as extended-reach links, single-photon detection, light detection and ranging, and high-performance computing.