A mechanism for catastrophic failure of avalanche diodes

A simple computer model of the dc electrical-thermal behavior of a Schottky-barrier GaAs IMPATT diode has been modified to include the effects of temperature-dependent thermal resistance. This has made possible the computation of dc V-I characteristics for various IMPATT diode designs and parameters. Computed terminal V-I characteristics, as well as E-J characteristics for points within the depletion layer invariably have shown successive regions of increasing, then decreasing, positive differential resistance, culminating in a region of negative differential resistance. According to an analysis of differential negative resistance appearing in the literature [5], it is a natural consequence of operation in a negative resistance region for high-current filaments to form. Furthermore, a phenomenological argument is cited to justify high-current filamentation in a region of decreasing positive resistance. Experimental evidence is advanced to support the contention that IMPATT shortouts are the natural consequence of diode operation beyond a differential resistance maximum, where the resistance, although positive, is decreasing and the formation of destructive high-current filaments is inevitable.