Enhancement of responsivity and speed in waveguide Ge/Si avalanche photodiode with separate vertical Ge absorption, lateral Si charge and multiplication configuration

Abstract

Waveguide-coupled Ge/Si separate absorption, charge and multiplication avalanche photodiodes (SACM APDs) have shown significant potential as high-sensitivity, low-noise, and high-speed photo-detection for optical communications. Here we present a nanoscale single-mode waveguide-integrated vertical Ge absorption, lateral Si charge and single multiplication configuration for a waveguide Ge/Si SACM APD. This device can achieve 90% absorption at 1550 nm wavelengths with a 10 μm-long Ge layer. The device exhibits a seven times reduction in device length compared to conventional waveguide structures and a 29% increase compared to multi-mode interference coupling. Meanwhile, a 3-dB bandwidth can achieve 47 GHz, which is five times higher than the conventional vertical Ge absorption, lateral Si charge and multiplication devices.