On theory nonlinear relaxation in polyaron sybsystem of polar semiconductors

Abstract

Kinetic equation for polaron subsystem of polar semiconductor is used for investigation of temperature and velocity relaxation in spatially uniform states. Phonon subsystem is assumed to be an equilibrium one. The relaxation processes are studied near their end with account for linear and quadratic ones. The theory introduces a new small parameter in the theory of relaxation. Its sense is justified by comparison of linear and nonlinear processes. Distribution function of the system is calculated approximately using method of truncated expansion of solutions of integral equation of the theory in the Sonine polynomials. Spectral theory of the linearized collision integral operator is used to proof existence and identity of solution of integral equations of the theory. It was obtained that local equilibrium approximation is true only one-polynomial approximation of the developed theory of the linear relaxation and is not valid in the theory of quadratic relaxation. A necessary condition of the validity condition of the developed theory is obtained as a restriction for the introduced small parameter.