Transient impact ionization in bulk Si [MOS devices]

The generation rate, G/sub ii/, due to impact ionization and the impact ionization coefficient /spl alpha/ in bulk Si are calculated from carrier distribution functions, solving the k-space Boltzmann transport equation. G/sub ii/ and /spl alpha/ are dependent on transients, and are not universal with respect to average energy, which facts originate in the different structures in k-space distribution function even at the same average energy. In such cases, the conventional relation of /spl alpha/J (where J is the current density) fails to predict G/sub ii/, so far as one takes /spl alpha/ for the steady-state /spl alphasub w/ defined as a function of average energy.<
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