Fig. 1. (a) Three-dimensional (3D) schematic and (b) cross-sectional view of the proposed sidewall doping Ge-Si photodetector. (c), (d) Simulated static optical field and electric field distribution in the Ge region for TE and TM modes. The bias voltage is −3  V. (e) Transmission electron microscopy (TEM) image of Ge-Si PD. (f) Optical micrograph of the Ge-Si PD. SSC, spot size conversion.

Fig. 2. (a) Current–voltage (I-V) characteristics of Ge-Si PD in the dark illuminated state. (b) Measured external and calculated internal responsivities of the Ge-Si PD for TE and TM modes in the C+L bands.

Fig. 3. (a) Dark current distribution of PD devices at different reticle sites under −3  V bias. (b) 3 dB bandwidth distribution of PD devices at different reticle sites under −3  V bias.

Fig. 4. Schematic of the experimental setup for measurement of the high-speed eye diagrams. The black and red lines represent optical and electrical connections, respectively. AWG, arbitrary waveform generator; EDFA, erbium doped fiber amplifier; VOA, variable optical attenuator; PC, polarization controller; PD, photodetector; TFLNOI MZM, thin film lithium niobate on insulator Mach–Zehnder modulator.

Fig. 5. Measured 100 Gbaud PAM-4 eye diagrams of TE and TM polarizations under a −3  V bias voltage at 1550 nm input wavelength. The time scale is 3 ps/Div. The voltage scale is 6 mV/Div.

Fig. 6. Measured 100 Gbaud PAM-4 eye diagrams at 1530, 1550, 1580, and 1610 nm input wavelengths. The time scale is 3 ps/Div. The voltage scale is 6 mV/Div.

Fig. 7. Measured 120, 130, 140, and 150 Gbit/s NRZ eye diagrams under a −3  V bias voltage. The time scale is 3 ps/Div.

Fig. 8. Measured 100, 112, 128, and 145 Gbaud PAM-4, and 100, 112, 128, and 136 Gbaud PAM-8 eye diagrams under a −3  V bias voltage with approximately 0.8 mA DC. The time scale is 3 ps/Div.