Avalanche characteristics of thin GaAs/Al0.6Ga0.4As heterojunction avalanche photodiodes

The mean multiplication gain and excess noise factor of thin GaAs/Al0.6Ga0.4As heterojunction avalanche photodiodes (HAPDs) are simulated. The ionization coefficients of electron and hole in bulk GaAs and Al0.6Ga0.4As are used in this model to study the role of heterojunction in reducing excess noise. The band-edge discontinuities at the conduction and valence bands are included in our model which may influence the number of carrier crossing the heterojunction and hence modifies the dead space in the HAPDs. The mean multiplication gain and excess noise factor with electron- and hole-initiated multiplication for 0.1 and 0.2 μm multiplication lengths in GaAs/Al0.6Ga0.4As HAPDs are shown. By considering the dead space effect, our model demonstrated a small noise mainly due to the localization of carrier ionization and the limited carrier feedback ionization at heterointerface. In our model, most of the ionizations occur in the first-initiated multiplication layer which reduces the randomness of carrier ionization and noise.