The luck drift model of impact ionization for superlattice structures incorporating a soft threshold energy

The threshold energy is said to be 'soft' if carriers can have kinetic energies greater than the threshold energy. The soft threshold phenomenon has been incorporated into the lucky drift model for superlattice structures and it has been found that the ionization coefficients are less than the corresponding bulk values in agreement with recent experimental work. The inclusion of a soft threshold has improved the agreement with some experimental data and where this is not the case reasons are offered. Work is in progress to improve the model further by the inclusion of barrier tunnelling.<
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