A simple model for avalanche multiplication including deadspace effects

A simple Monte Carlo model (SMC) using single effective parabolic valleys a nd accurately accounting for deadspace effects is presented for calculating the avalanche process. Very good agreement is achieved with a range of mea sured electron and hole multiplication results from GaAs p(+)-i-N+'s with i -region thicknesses, w, from 1 mu m down to 0.025 mu m and with the excess noise factors down to 0.05 mu m. While the results are insensitive to the p recise values of input parameter for structures with w greater than or equa l to 0.2 mu m, this is not the case in thinner structures where the deadspa ce represents a significant fraction of the device. For w < 0.2 mu m, the e nergy dependence of the ionization rate becomes increasingly important. The SMC model is tested against a full-band Monte Carlo model (FBMC) by compar ing the mean distance between ionization events and the probability density functions, which are effectively the histograms of distances between ioniz ation events, for equivalent material parameters, The good agreement betwee n these suggests that the SMC, with a relatively small number of fitting pa rameters and much faster calculation times than the FBMC, is a useful tool for device simulation and interpreting experimental results.