An ensemble Monte Carlo simulation is presented to investigate the avalanche multiplication process in thin InP avalanche photodiodes(APDs).Analytical band structures are applied to the description of the conduction and valence band,and impact ionization is treated as an additional scattering mechanism with the Keldysh formula.Multiplication gain and excess noise factor of InP p+-i-n+ APDs are simulated and obvious excess noise reduction is found in the thinner devices.The effect of dead space on excess noise in thin APD structures is investigated by the distribution of impact ionization events within the multiplication region.It is found that the dead space can suppress the feedback ionization events resulting in a more deterministic avalanche multiplication process and reduce the excess noise in thinner APDs.
