Current filament patterns in n-GaAs layers with different contact geometries

In thin n-GaAs epitaxial layers current filament patterns formed by low-tem perature impurity breakdown have been visualized for different contact geom etries. Independent of the contact geometry, after nucleation a generic sha pe of filaments has been observed in the form of a stripe of high current d ensity with parallel borders whose width is proportional to the sample curr ent. Filament splitting processes could be attributed to geometrical proper ties of the contacts without any inherent critical width. In a magnetic fie ld applied normal to the semiconductor film two different types of stable f ilament configurations have been found. One can be characterized by a filam ent deflection in the direction of the Lorentz force acting on the;electron s, the other one by a filament tilting related to the Hall angle. The exper imental results are explained in terms of a simple mathematical model.