High-speed waveguide lateral Ge/Si avalanche photodetector for C-band and L-band

Germanium/silicon (Ge/Si) avalanche photodiodes (APDs) have been intensively investigated and are widely used in various fields, such as near-infrared detection and quantum communication. However, existing research of Ge/Si APDs mostly focuses on a single optical communication band. The influence of wavelengths has not been studied. In this paper, we propose a lateral separate absorption multiplication (SAM) APD and conduct an in-depth research into the performance of Ge/Si APDs at different wavelengths. We reveal a significant enhancement in the performance of Ge/Si APDs at L-band (1600 nm) compared to the C-band (1550 nm). A gain-bandwidth product of 279 GHz corresponding to a gain of 18.4 and a bandwidth of 15.2 GHz are achieved at 1600 nm. Through systematic experimental design and theoretical analysis, we evaluate the mechanisms of the higher gain, providing insights into its potential applications in the field of optical communication. This study holds significant implications for expanding the application scope of Ge/Si APDs in optical communication, providing experimental support for their superior performance at higher wavelengths and potentially driving advancements in related technologies.