Self-organized symmetry-breaking current filamentation and multistability in Corbino disks

A complex symmetry-breaking current instability in doped semiconductors induced by low-temperature impact ionization breakdown is investigated. We present computer simulations revealing the dynamics of the self-organized formation of multiple current filaments in n-GaAs Corbino disks, i.e., samples with concentric circular contacts. Our results explain the nascence of a filament in terms of two consecutive stages: a radially symmetric impact ionization front spreading from the inner contact becomes unstable and breaks up into a number of streamers evolving into prefilaments. With rising current, competition between those prefilaments takes place due to the global coupling via the load resistance. Only a small number of these survive and grow into fully developed filaments. Using the applied bias as a control parameter we find multistability and hysteresis, with jumps in the current-voltage characteristic caused by the spontaneous formation of additional filaments in the Corbino disk.