Stationary State of a Semiconductor with Negative Bulk Differential Conductivity

The system of nonlinear equations describing the stationary state of a semiconductor with negative bulk differential conductivity is analysed in the “phase plane”. The negative differential conductivity is considered to arise from either the field dependence of the electron concentration (due to the recombination process) or the field dependence of the mobility. Possible spatial variations of the field along the sample have a step-like form and correspond to two different values of the saturation current. The current-voltage characteristics and the field distributions are studied experimentally in n-type germanium samples containing partly compensated copper. It is found that the saturation current corresponds to the peak of the current-field curve of a spatially homogeneous sample. The electric field in the low and high field regions, as well as the location of these regions in the sample, are found to be in satisfactory agreement with theory. [Russian Text Ignored].