We present a Full-Band Monte Carlo (FBMC) investigation of impact ionization in GaAs p-i-n Avalanche Photodiodes (APDs). FBMC simulations have been used to compute the gain and the excess noise factor and a new equation has been derived for the extraction of history-dependent impact ionization coefficients from FBMC simulations. Results from FBMC are then compared with the ones of nonlocal historydependent impact ionization models. We found that at high reverse bias voltages it is important to take into account the fact that secondary carriers are generated with nonzero kinetic energy. Finally, we propose an improved history-dependent model using an energy-dependent mean free path.
