High-speed Avalanche Photodiodes based on III-V Compounds for Optical Communications

Avalanche photodiodes based on III-V-compounds feature flexibility in designing bandwidth, gain, responsivity, and linearity, which are associated with not only the thickness of each layer but also doping profiles and material options and their combinations. Here, we review the design and performance of our high-speed avalanche photodiodes that feature a unique epitaxial layer structure. Even though the APDs have a vertical illumination structure, which is essential for easy optical coupling and fabrication, their speed is high enough for operation with 100G-PAM4. We also discuss our efforts for improving linearity, which is important for operation with higher-order modulation format.