  The current (voltage) responsivity of the superlattice-based diode detectors
in the terahertz frequency band which includes the region of the polar optical
phonon frequencies has been analyzed theoretically. Within the framework of the
equivalent circuit approach an electro-dynamical model which allows one to
analyze the responsivity taking into account the plasmon polariton excitation
both in the substrate and in the contact layers of the diodes has been
suggested. It has been shown that the presence of the plasmon polariton
excitation gives rise to strong features in the frequency dependence of the
superlattice-based diodes responsivity, i.e. to the resonance dips and peaks at
frequencies of hybridized plasmons and optical phonons. It has been suggested
that by judicious engineering of the superlattice-based diodes it would be
possible to enhance substantially their responsivity in the terahertz frequency
band.
