IMPACT IONIZATION MODEL FOR FULL BAND MONTE-CARLO SIMULATION

The impact ionization rate in silicon is numerically derived from wave functions and energy band structure based on an empirical pseudopoten tial method. The calculated impact ionization rate is well fitted to a n analytical formula with a power exponent of 4.6, indicating soft thr eshold of impact ionization rate, which originates from the complexity of the Si band structure. The calculated impact ionization rate shows strong anisotropy at low electron energy (epsilon < 3 eV), while it b ecomes isotropic at higher energy. Numerical calculation also reveals that the average energy of secondary generated carriers depends linear ly on the primary electron energy at the moment of their generation. A full band Monte Carlo simulation using the newly derived impact ioniz ation rate demonstrates that calculated quantum yield and ionization c oefficient agree well with reported experimental data.