High-Speed 850 nm Photodetector for Zero-Bias Operation

High-speed photodetector operating at 850 nm wavelength with a large diameter and high quantum efficiency is desirable to meet the growing demands of short-reach optical links for high-performance computing systems. Zero-bias operation of the high-speed photodetectors can reduce power consumption, minimize system complexity of the optical transceivers and reduce the radiation damage in a harsh environment. Traditional p-i-n photodetectors for 850 nm applications often require a high reverse bias to accelerate the carrier transport for high-speed data transmission. In this work, we demonstrate a high-speed and low dark current modified uni-traveling-carrier photodiode based on GaAs/AlGaAs at 850 nm wavelength operating under zero bias with a quantum efficiency of 73%. The 3-dB bandwidth of the 20 μm and 40 μm diameter devices is 22.5 GHz and 13.3 GHz, respectively. A clear eye pattern is demonstrated at a 25.8 Gbit/s data rate for the device under zero-bias operation. To the best of our knowledge, this photodetector demonstrates the highest 3-dB bandwidth among all the zero-bias 850 nm photodetectors reported to date.