Waveguide-Integrated Ge/Si Avalanche Photodiode with Vertical Multiplication Region for 1310 nm Detection

Ge/Si separate absorption, charge, and multiplication avalanche photodiodes (SACM APDs) coupled with waveguides have shown significant potential as high-sensitivity, low-noise, and high-speed photodetectors for optical communications. In this study, we present a waveguide-integrated Ge/Si SACM APD fabricated on an eight-inch silicon photonics platform. The device exhibits a primary responsivity of 0.68 A/W at the unit gain voltage of 6 V for the O-band (1310 nm) wavelength, with a 10 μm-long and 1 μm-wide Ge layer. Additionally, the device demonstrates a 3 dB bandwidth of 25.7 GHz, with an input optical power of −16.8 dBm. The largest gain bandwidth product (GBP) is 247 GHz at a gain of 9.64 and a bias voltage of 15.7 V. The eye diagram is open at the bias voltage of 16 V, with a capacity to receive 28 Gbps of data. This APD shows potential for application in high-speed data transmission systems.