Fig. 1. Three-dimensional schematic of the Ge-on-Si positive-intrinsic-negative (PIN) waveguide photodetectors with the (a) single-injection structure, (b) dual-injection structure, and (c) waveguide structure in the layout.

Fig. 2. Top view of the light-field distribution in the Ge absorption layer of the (a) single- and (b) dual-injection photodetectors by the FDTD method; the red box represents the Ge-absorption area.

Fig. 3. Measured photocurrent as a function of the input light power at 1550 nm for both single- and dual-injection photodetectors.

Fig. 4. Threshold-enhanced image of the saturated light power in the Ge-absorption layer under different incident light power; the white zone represents the saturation area. The saturation threshold is 2×10−4. (a) Single-injection photodetector. (b) Dual-injection photodetector.

Fig. 5. Different bandwidth curves of the dual- and single-injection photodetectors with the increase in the incident light power. The red curve indicates the bandwidth of the single-injection photodetector, and the black curve indicates that of the dual-injection photodetector.