Novel three-electrode Ge/Si balanced avalanche photodetector for FMCW LiDAR application

Due to the outstanding anti-interference capability against the ambient noise, LiDARs based on frequency-modulated continuous wave (FMCW) technology with high sensitivity and high signal-to-noise ratio (SNR) are essential to achieve ideal photodetection of weak light. To significantly improve the weak light detection performance of balanced photodetectors, this work first demonstrates a novel near-infrared germanium-on-silicon (Ge/Si) avalanche photodetector with a three-electrode balanced scheme. The single three-electrode avalanche photodetector exhibits a high responsivity of >200 A/W near breakdown voltage. The three-electrode balanced avalanche photodetector (3ele-BAPD) achieves a common-mode rejection ratio (CMRR) of 50 dB at an operating wavelength of 1550 nm. We have set up the FMCW coherent detection system. The minimum detectable power of −93 dBm can be achieved, corresponding to an SNR of 3.2 dB and a detection probability of 54%. In comparison, the performance exceeds that of the two-electrode balanced avalanche photodetector (2ele-BAPD), which exhibits a minimum detectable power of −85 dBm with a corresponding SNR of 3.1 dB and a detection probability of 51%. The superior weak light detection performance enables the 3ele-BAPD to accomplish 3D imaging based on the FMCW LiDAR scheme. Moreover, the 3ele-BAPD is also applied to velocity measurement for 4D sensing. The applications of LiDAR velocity measurement and imaging are verified.