Fig. 11

a Schematic and b electric field distribution of the lateral p-i-n APD with double heterojunctions [79]; c Schematic cross section of the waveguide-coupled Si-Ge p-i-n APD. Insets are cross-sectional views of the p-i-n device and the injection waveguide [80]; d Schematic of the p-i-n APD with lateral p-i-n heterojunctions, optical mode profiles of p-i-n APDs with various germanium widths, and light propagation through p-i-n APDs with various germanium lengths [116]