Screening due to non-equilibrium carriers in presence of deep repulsive traps

The characteristics of screening length due to non-equilibrium electrons at low lattice temperatures are investigated theoretically, when the lifetime of the carriers is controlled by deep repulsive traps. The calculations have been made covering a wide range of the electric field, starting from a weakly heated carrier ensemble up to the onset of impurity breakdown. Apart from becoming field dependent, the screening length now shows a rather complicated dependence upon the lattice temperature. The numerical results for high-purity covalent semiconductors like Ge and Si show that the characteristics of the screening length are now significantly different from what one obtains for an ensemble of carriers that is in thermodynamic equilibrium with the lattice atoms.