Quenching of impact ionization in heavy ion induced tracks in wide bandwidth Si Avalanche Photodiodes

High-injection effects on the impulse response and high-frequency gain of a Si Avalanche Photodiode have been observed for a series of MeV heavy ions species with the same track structure but different injection levels. Focused picosecond laser results have also been collected as a function of laser waist. For the ultra-high injection levels present in the ion track, space-charge screening distorts the field profile leading to reduced impact ionization rates. Synopsis TCAD simulations are performed to clarify the role of screening in quenching or enhancing avalanche mechanisms and under what conditions one occurs over the other for an APD.