THEORY OF ELEMENTARY EXCITATIONS OF THE MAGNETOPLASMA IN SEMIINFINITEN-I-P-I SUPERLATTICES

A theoretical investigation has been made of the collective (bulk and surface) excitations in a semi-infinite superlattice system made up of n- and p-type doped semiconductors separated by an undoped intrinsic (i) semiconductor (n-i-p-i superstructure). An external magnetic field is assumed to be oriented perpendicular to the interfaces and to the direction of propagation. The thicknesses of the constituent layers ar e assumed to be sufficiently large that quantum-size effects can be ig nored. The material layers are characterized by frequency- and magneti c-field-dependent dielectric functions. The magnetoplasma modes are de fined by electromagnetic fields that are localized at and decay expone ntially away from the interfaces and from the end of the superstructur e. The general dispersion relations are derived using a fully retarded theory in the framework of a transfer-matrix method. Numerical exampl es, both with and without an applied magnetic field, are presented for several illustrative cases.