Nonlinear mechanisms for self-focusing of microwaves in semiconductors

Abstract

A detailed investigation of various possible mechanisms of nonlinear self‐focusing of electromagnetic waves in semiconductors has been made. In uncompensated semiconductors focusing is possible only due to mass modulation. However, in a semiconductor in which electron‐ to hole‐concentration ratio is equal to the square of the mass ratio, free‐carrier diffusion provides an additional effective mechanism for self‐focusing. In both mechanisms thermal effects are much more important than the drift effects. When the duration of the signal is comparable with the free‐carrier energy‐relaxation time (which is ∼ 10⁻⁸ sec in InSb at low temperatures) its shape becomes distorted to a considerable extent, and the distortion provides a direct method for the detailed investigation of energy‐relaxation mechanisms.