The general theory of parametric coupling between space-charge waves and dr
ifting charge carriers in thin-film semiconductor structures has been worke
d out. This theory is applicable, in particular, to n-GaAs and n-InP semico
nductors with negative differential conductance due to intervalley electron
transitions under high electric fields. We started from the electrodynamic
theory of waveguide excitation by extraneous currents, which was extended
for arbitrary waveguide structures with composite active media. Our theory
makes it possible to study parametric interaction between space-charge wave
s in semiconductor films with regard for boundary conditions, diffusion, th
e anisotropy and the frequency dispersion of the differential electron mobi
lity, as well as the multifrequency and multimode nature of a wave process
in thin-film structures. (C) 2000 MAIK "Nauka/Interperiodica".