Abstract. We present experimental investigations on the spatio-temporal nonlinear current flow in the post-breakdown regime of p-germanium at liquid-helium temperatures. The basic nonlinear effects are characterized in terms of the underlying semiconductor physics, taking into account the influence of different experimental parameters. 05.45. + b, 72.20.Ht, 72.70. + m It is well known that a large number of physical and nonphysical systems show spontaneous formation of spatial or temporal structures as a result of instability. Close to such instability points the dynamics of the system and its emerging structures are determined by a set of, in general, a few collective variables, often called order parameters. The underlying synergetic approach introduced by Haken [1] can explain the unexpected order and coherence arising on the macroscopic scale, regardless of the large number of competing physical forces interacting on the microscopic scale. Motivation for the intensive study of cooperative dynamics and pattern formation phenomena during the past few years derives from an increasing appreciation of the remarkable diversity of behavior encountered in nonlinear systems and of universal features shared by entire classes of similar nonlinear dynamic processes.
PACS:So far, it appears that the subject of such complex nonlinear behavior is dominated by theoretical investigations and computer studies, whereas experimental measurements on real physical systems represent the minority. Among the various objects which can be studied experimentally, solid-state turbulence in semiconductors appears particularly interesting [2]. Nonlinear current transport behavior during lowtemperature avalanche breakdown of extrinsic germanium comprises the self-sustained development of spatio-temporal dissipative structures in the formerly homogeneous semiconductor [3]. This kind of nonequilibrium phase transition between different conducting states results from the autocatalytic nature of impurity impact ionization generating mobile charge carriers [4]. The simple and direct experimental accessibility via advanced measurement techniques favors semiconductors as a nearly ideal study object for complex nonlinear dynamics compared to other physical systems. Further representing a convenient model reaction-diffusion system that exhibits distinct universal features, the present semiconductor system may acquire general significance for many synergetic systems in nature. Finally, in view of the rapidly growing application of semiconductor technologies, the understanding, control, and possible exploitation of sources of instability in these systems have considerable practical importance. This paper gives a classification of our experimental investigations on the spatio-temporal nonlinear current flow in the post-breakdown regime of p-germanium at liquid-helium temperatures. Section 1 briefly outlines an example of a set of nonlinear current instabilities obtained from our semiconductor system. Section 2 reports the characterization of the basic...