25 Gbps low-voltage waveguide Si–Ge avalanche photodiode

Abstract

Silicon-germanium (Si–Ge)-based avalanche photodiodes (APDs) have shown a significant improvement in receiver sensitivity compared to their III–V counterparts due to the superior impact ionization property of silicon. However, conventional Si–Ge APDs typically operate at high voltages and low speed, limiting the application of this technology to data communication. In this paper, we present a waveguide Si–Ge avalanche photodiode using a thin silicon multiplication region with a breakdown voltage of −10 V, a speed of 25 GHz, and a gain-bandwidth product (GBP) of 276 GHz. At 1550 nm, sensitivities of −25 dBm and −16 dBm are achieved at 12.5 Gbps and 25 Gbps, respectively. This design will enable implementation of Si–Ge APDs for optical interconnects in data centers and high-performance computers, allowing significant reductions in aggregate system laser power (and therefore cost).