ELECTRON AND HOLE IMPACT IONIZATION COEFFICIENTS AT VERY HIGH ELECTRIC FIELDS IN SEMICONDUCTORS

We have fitted the soft lucky drift model of impact ionization of Ridley to exper-imental data for GaAs, InP, Si, Ge and In0.47Ga0.53As semiconductors. Excellent fits of the theory to experimental data were obtained by using least-squares fitting algorithm. A generalized Keldysh formula has been used to introduce a soft thresh-old factor. Generalized Keldysh formula originates from realistic energy bands in semiconductors at high electric field which reflects the density of states of energy bands. Keldysh factor and a new mean free path are calculated. A comparison with reported values of both Ridley and Marsland showed reasonable agreement for mean free path, but there are still large differences among Keldysh factors