Ultra‐Large Bandwidth and Ultra‐High Sensitivity Germanium/Silicon Avalanche Photodiode

Abstract Germanium/silicon (Ge/Si) avalanche photodiode (APD) has emerged as a highly desirable component for optical communication, sensing, and computing, attributed to its inherent gain. Conventional schemes typically suffer from limited bandwidth and significant excess noise due to the high gain, restricting the high‐sensitivity detection in burgeoning high‐speed applications. Here, a Ge/Si APD is developed with an ultra‐large bandwidth at an optimal gain. This breakthrough is achieved by implementing an extremely narrow multiplication layer to enhance the space charge effect, overcoming the intrinsic bandwidth limitation in conventional APDs while elaborately harnessing the gain to a moderate value to ensure the optimal sensitivity. The device possesses a bandwidth of 67 GHz at an optimal gain of 6.6 and enables data reception of 240 Gb s −1 four‐level pulse amplitude modulation signal—the largest bandwidth and highest single‐channel bitrate among all reported APDs. The presented APD suggests promising applications for high‐speed and high‐sensitivity data communication owing to its competitive performance, cost‐effectiveness, and high‐yield production.