Process Optimization and Microwave Model of GaAs Photodiodes for 50 Gb/s Optical Links

GaAs photodiode is a critical O/E receiver component for high-speed optical link in data centers and HPC. In this work, GaAs P-i-N photodiodes with four different aperture diameters are developed for 50 Gb/s data detection. Device layer structure and the fabrication process are optimized to achieve low dark current, high responsivity and high bandwidth. An O/E microwave model based on the device physics and structure is developed and the simulated frequency responses agree well with the measurements. The 50 Gb/s NRZ eye-diagrams of optical link test are validated via the use of 20 and 25 μm diameter photodiodes and a 29 GHz 850 nm oxide VCSEL.