CURRENT STRUCTURES IN SI-ZN

The formation of complex spatial distributions of the electric current in high-resistivity zinc-doped silicon has been studied. These distri butions were obtained employing a system formed by the semiconductor a nd a discharge gap. Instabilities of spatially nonuniform distribution s resulting in the formation of multiple current filaments with increa sing voltage above the critical value have been observed. The resultan t distributions were visualized using a thin gas-discharge gap distrib uted along the cross section of a sample. Under the experimental condi tions the discharge gap played only a passive role and was not respons ible for the appearance of the electric-current structures. All the cu rrent filaments were identical and their transverse cross sections wer e complex because of the crystal symmetry. A system containing filamen ts exhibited a hysteresis of the global current-voltage characteristic and multistability of the total current. In the range of existence of the filaments the total current was approximately proportional to the cube of the electric field in the sample. These observations were exp lained phenomenologically by activator-inhibitor models describing the formation of structures in distributed active media characterized by diffusion. The preliminary experimental data led to the suggestion tha t the activation stage of the filamentation of the current was the res ult of double injection of carriers into the bulk of the sample, and t hat the temperature of the sample acted as an inhibitor of this proces s.