High-performance waveguide-integrated Ge/Si avalanche photodetector with small contact angle between selectively epitaxial growth Ge and Si layers

Du Xiao-Qian^{1, 2}, Li Chong³, Li Ben³, Wang Nan^{1, 2}, Zhao Yue^{1, 2}, Yang Fan^{1, 2}, Yu Kai^{1, 2}, Zhou Lin^{1, 2}, Li Xiu-Li^{1, 2}, Cheng Bu-Wen^{1, 2}, Xue Chun-Lai^{1, 2, †}

(a) The top view of the fabricated device with the step-coupler length of 3.0 μ m and the Ge length of 20 μ m ; (b) the schematic cross-sectional view of the waveguide Ge/Si SACM-APD.