Dispersion Relation for Two-Valley QuasiHydrodynamic Models in SCWs Propagation in n-GaAs Thin Films

The space charge wave propagation in thin n-GaAs films has been considered within a framework of different quasi-hydrodynamic balance models. A comparative study of the dependencies k(omega) of a complex longitudinal wave number on frequency, which are obtained from different balance equation models are presented and discussed. It has been demonstrated that the model where the balance equations are written for different valleys directly seems to be the most correct. The balance models based on averaging over the valleys may lead to incorrect results in the case of long distances of propagation of space charge waves. When the thermal conductivity term is taken into account and the length of the system is short, the averaged balance models can get satisfactory results