Photon‐assisted avalanche spreading in reach‐through photodiodes

We have investigated the spreading of the avalanche process over the area of reach‐through avalanche photodiodes operated in Geiger mode. A comparison between the measurements and the results of a computer simulation suggests that photons emitted from hot carrier relaxations play the dominant role in the avalanche dynamics. It is the randomness of the photon‐assisted process which impairs the performance of these detectors in timing measurements.