Waveguide-coupled uni-traveling-carrier lateral photodetector with Gaussian gradient germanium doping and DBR

To address the demands of microwave photonic links for broadband and high dynamic range. We propose a germanium(Ge) waveguide-coupled uni-traveling-carrier lateral photodetector (UTC-L PD) targeting performance degradation constraint between bandwidth and saturation power under high optical input power. This PD utilizes Gaussian gradient doping to form a partially depleted absorber(Ge), blocking photogenerated electron diffusion while avoiding hole accumulation. The structure achieves up to 70 GHz bandwidth and maintains a 25 GHz high-speed response under 10 mW optical input power. The saturation power reaches approximately 30 mW. We further designed a distributed Bragg reflector (DBR) structure along the light propagation direction to enhance responsivity by fully utilizing optical absorption, achieving a high responsivity of 0.77 A/W at -3 V bias.