1：Experimental Design and Method Selection:

The device is designed with a lateral SACM (Separate Absorption Charge Multiplication) configuration, utilizing Ge and Si as the absorption and avalanche multiplication regions respectively. The doping profile for the charge region was optimized using TCAD simulations to achieve high E-field in the multiplication region while maintaining enough E-field in Ge to extract photogenerated carriers.

2：Sample Selection and Data Sources:

The device consists of a 0.5 μm wide and 14.2 μm long Ge waveguide, fabricated on a 200 mm SOI wafer with 220 nm top Si layer on 2 μm thick buried oxide (BOX).

3：5 μm wide and 2 μm long Ge waveguide, fabricated on a 200 mm SOI wafer with 220 nm top Si layer on 2 μm thick buried oxide (BOX). List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Agilent 50 GHz light wave component analyzer (N4373C), Agilent 50 GHz vector network analyzer (N5225A), Anritsu MU1812020B pulse pattern generators, MP1821A 50G/56G Gbps MUX, LiNbO3 modulator, 60 GHz RF probe, bias-Tee, 60 GHz Agilent remote sampling head, 80 GHz Agilent sampling scope.

4：Experimental Procedures and Operational Workflow:

Static measurements were carried out at room temperature to characterize the device's I-V characteristics and responsivity. Small signal RF measurements were performed to extract the 3 dB opto-electrical bandwidth and avalanche gain. Large-signal response was measured using pseudorandom binary sequence signals at 25, 40, and 50 Gbps data rates in NRZ-OOK modulation format.

5：Data Analysis Methods:

The responsivity of the APD was calculated by extracting the photocurrent and dividing it by the estimated optical power in the Si waveguide. The avalanche gain was estimated from the ratio of responsivity at high voltage over the responsivity at low voltage.