All-Silicon Waveguide Avalanche Photodetectors With Ultrahigh Gain-Bandwidth Product and Low Breakdown Voltage

We investigate the avalanche effect in 250 μm long silicon waveguides integrated with periodically interleaved p-n junctions. The surface state absorption is enhanced by reducing the waveguide width. Upon a bias voltage of -5.9 V, the measured responsivity is 2.33 A/W with a dark current of 0.78 μA. The avalanche gain is 284 and the 3-dB bandwidth is 3.6 GHz, leading to an ultrahigh gain-bandwidth product of 1.02 THz. The avalanche photocurrent is stable with time below -6 V when ~1 mW on-chip optical power is launched. The photodetector has a linear response to optical power and can be readily integrated with other silicon photonic devices.