DOUBLE-INJECTION LIMIT IN A SEMICONDUCTOR WITH A FALLING DEPENDENCE OF LIFETIME ON THE ELECTRIC FIELD.

Double-injection currents are calculated for injection contacts with high emissivity into a semiconductor (or insulator) in which the nonequilibrium carrier recombination probability increases rapidly with the electric field E. The cases of monomolecular recombination and impact interband recombination are considered separately. It is found that injection is possible in the first case only in sufficiently short samples and has not one but two current-voltage characteristics vertical at the saturation voltage. In the second case, the characteristic exists only for limited range of currents, and forms a closed loop. These results are analyzed in terms of a negative differential conductance (NDC) ″latent″ in the homogeneous state and ″manifest″ in bounded samples with appropriate boundary conditions.