High-Responsivity Waveguide UTC Photodetector with 90 GHz Bandwidth for High-Speed Optical Communication

A directly coupled waveguide uni-traveling carrier photodetector (UTC-PD) with high responsivity and broad bandwidth is demonstrated. The device’s epitaxial structure was carefully optimized via optical simulations to enhance quantum efficiency. Furthermore, the fabrication process was refined to introduce a vertically defined mushroom-shaped mesa structure, which effectively maintains high responsivity while facilitating further improvement in bandwidth performance. As a result, the fabricated device, without the use of an anti-reflection coating, simultaneously achieves a responsivity of 0.49 A/W and a 3 dB bandwidth of 90 GHz.