Ge/Si avalanche photodetectors with high gain-bandwidth product

We report a normal incidence Ge/Si avalanche photodiode with separate-absorption-charge-multiplication (SACM) structure by selective epitaxial growth. By proper design of charge and multiplication layers and by optimizing the electric field distribution in the depletion region to eliminate germanium impact-ionization at high gain, a high gain-bandwidth product of 310 GHz has been achieved at 1550 nm.