High-sensitivity and high-bandwidth receivers are always demanded for high-speed optical link systems. As a key element, an avalanche photodiode (APD) is often regarded as one of the most attractive options for achieving high sensitivity owing to the potential high internal gain. In this paper, a 48-GHz waveguide Ge/Si avalanche photodiode operating at the O-band (1310 nm) is designed with a lateral reach-through structure and fabricated with simplified processes. The fabricated APD shows a high primary responsivity of 0.93 A/W at the unit-gain voltage of − 4.7 V . It has an avalanche gain of 12.8 and a record gain-bandwidth product of ∼ 615 GHz with an input optical power of − 15 dBm when operating at a bias voltage of − 14 V . The present Ge/Si APD is used successfully for high-speed data receiving, showing a sensitivity improvement about 7.6 dB for KP4-FEC operation (i.e.,  BER = 2.4 × 10 − 4 ) with 50 Gbps non-return-to-zero (NRZ) data, compared with the case of using the reference PIN PD on the same chip. The sensitivity of the receiver with the present APD for NRZ signals is about − 21.3 dBm , − 17.8 dBm , and − 12.6 dBm for KP4-FEC operation with different data rates of 50 Gbps, 80 Gbps, and 100 Gbps, while the sensitivity for four-level pulse amplitude modulation signals is about − 13.2 dBm and − 11.3 dBm for KP4-FEC operation with different data rates of 25 and 50 Gbaud. Such high-performance APDs pave the way to achieve high-speed and high-sensitivity data transmissions.

A high-performance waveguide Ge/Si avalanche photodiode operating at the O-band (1310 nm) is designed with a Ge/Si ridge waveguide defined by two shallow trenches in the active region and fabricated with simplified processes. The device shows a high primary responsivity of 0.96 A/W at the unit-gain voltage of −7.5 V. It has a large 3-dB bandwidth of >27 GHz and a low dark current of 1.8 µA at a reverse bias voltage of −13 V. When the present Ge/Si APD is used for receiving 25 Gbps data, the eye-diagram is open even for an optical power as low as −18 dBm. Furthermore, 50 Gbps data receiving is also demonstrated with an input optical power of −15 dBm, showing the great potential of the present Ge/Si APD for the application in future high-speed data transmission systems.

A high-performance waveguide Ge/Si avalanche photodiode is designed and fabricated with simplified processes, showing a high primary responsivity of 0.96 A/W, a 3dB bandwidth of 27 GHz. A 50 Gbps data transmission is also demonstrated.