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) Simulated absorption for the step-coupler structure with Ge length of 20 μ m , thickness of 1 μ m , and width of 5 μ m as a function of L-step; (b) responsivity of the two step-coupler (length of 1.5 μ m and 3.0 μ m ) devices versus different bias voltages; (c) cross-sectional view of electric field intensity E in a structure of step-coupler length of 3.0 μ m .