CONTACT EXCLUSION IN A NONUNIFORM ELECTRIC-FIELD - CASE OF A CYLINDRICAL SAMPLE

The current-voltage characteristics and the spatial distribution of the carrier density and the electric field in a hollow-cylinder sample are studied theoretically and experimentally. Antiblocking contacts are applied to the inner and outer surfaces of the cylinder. In the case of exclusion from the inner radius, the current-voltage characteristic may not have a region in which the current I is proportional to the square root of the applied voltage V. Such a region is characteristic of exclusion in a plate. In the cylindrical case the current-voltage characteristic becomes linear, with a conductivity determined by the concentration of ionized impurities, immediately after the beginning of the high level of exclusion. The exclusion length L(e) depends on the current in accordance with L(e) proportional-to I1/2. Upon exclusion from the outer surface of the cylinder, the distribution of the electric field in the sample may have two maxima. The experiments used p+-p-p+ structures of Ge in the temperature region of intrinsic conductivity.