High Speed Waveguide Uni-Traveling Carrier InGaAs/InP Photodiodes Fabricated By Zn Diffusion Doping

Photodiodes (PDs) which convert optical signals to electrical signals have been widely used in many fields. In contrast to pin PDs, in uni-traveling carrier (UTC) PDs, the absorption layer is p type doped and only photo-generated electrons are transported, which results in several superior characteristics including super high speed operation, high saturation current and low voltage operation. In this work, high speed InP based waveguide UTC-PDs have been fabricated by Zn diffusion doping for the first time to our knowledge, in contrast to the in situ doping of previous UTC-PDs. Diffusion doping will make it much easier for the UTC-PDs to be integrated with high quality passive waveguide and multi-quantum well (MQW) based active devices for photonic integrated circuit (PIC) applications. UTC-PDs with 3 × 15, 3 × 25 and 3 × 50 μm ² absorption areas are fabricated, all having over 50 GHz bandwidth at -1V bias voltage. At -3 V bias, the RF power at 40 GHz shows no saturation at up to 17 mA photocurrent for the 3 × 25 μm ² PD.