Small-signal computer simulation of IMPATT diodes including carrier diffusion

A generalized computer simulation method for small-signal analyses of IMPATT diodes incorporating the carrier diffusion current is presented. The method is capable of predicting the effect of carrier diffusion on the integrated device's microwave characteristics as well as on individual space-step contributions to diode negative resistance which in turn can identify the diode zone where carrier diffusion would have a pronounced effect. The results of author's investigation on the effect of carrier diffusion on performance of silicon flat-profile p + nn + , n + pp + and n + npp + diode structures indicate that diffusion has a pronounced effect on the p-side of the diodes whereas its effect on the n-side is only marginal. The changes in the values of diode negative conductance and diode negative resistance of the silicon flat-profile double-drift region diodes are observed to remain within ten per cent if the frequency of operation is kept within 100 GHz.