Abstract
Photodetectors with broad spectral response and high responsivity demonstrate significant potential in optoelectronic applications. This study proposes a Si/Ge avalanche photodiode featuring nanostructures that enhance light absorption. By optimizing the device epitaxial structure and these nanostructures, a wide spectral responsivity from 0.4 to 1.6 μm is achieved. The results demonstrate that introducing surface photon-trapping nanoholes and SiO(2) reflective grating nanostructures increases the average light absorptivity from 0.64 to 0.84 in the 0.4-1.1 μm range and from 0.31 to 0.56 in the 1.1-1.6 μm range. At an applied bias of 0.95 V(br-apd), the responsivity reaches 17.24 A/W at 1.31 μm and 17.6 A/W at 1.55 μm. This research provides theoretical insights for designing high-responsivity photodetectors in the visible-near-infrared broadband spectrum.