PROPAGATION OF THERMAL PERTURBATIONS IN PHOTOINJECTED PLASMA IN SEMICONDUCTORS - 2ND SOUND-WAVES

The propagation of thermal perturbations in the carrier system in a highly photoexcited plasma in direct-gap polar semiconductors is considered. In a hydrodynamic approach based on the so-called informational statistical thermodynamics, an equation of evolution for the energy flux that extends the usual Fourier's constitutive equation is derived. In conjunction with the equation of evolution for the energy, a hyperbolic (telegraphist like) equation of evolution for the quasi-temperature is derived, that implies in damped wave propagation, corresponding to propagation of second sound. Numerical calculations appropriate for GaAs are presented, and the transition from wave to diffusive motion and the expected Raman spectrum are discussed.