Dead space effect on excess noise factor in double heterojunction avalanche photodiodes

A double heterojunction avalanche photodiode (DHAPD) model using Monte Carlo (MC) method is applied to study the effect of dead space on excess noise factor. The mean multiplication gain and excess noise factor involving electron and hole impact ionizations are simulated in our work. The higher order impact ionization occurs in three multiplication layers is considered in the model. The avalanche characteristics of DHAPD are obtained by incorporating the dead-space, d ij , hole to electron coefficients ratio, k j and heterointerface probability, p im . Among these factors, the dead space effect plays an important role in reducing the excess noise factor in thin DHAPD. The dead space effect is also known in minimizing noise in homojunction APD when the device length is getting smaller. The distributions of carriers in multiplication region are demonstrated to explain the effect of dead space in DHAPD. Meanwhile, it is also shown that the hole to electron ionization coefficients ratio, k 2 =0.1 in the second layer gives the small excess noise factor in designing the DHAPD.