Intrasubband plasmons in semi-infinite n-i-p-i semiconductor superlattices

A theoretical investigation has been made of the collective intrasubband plasma modes in a semi-infinite superlattice system consisting of n- and p-type doped semiconductors separated by an undoped intrinsic (i) semiconductor (n-i-p-i superstructure). The thicknesses of the constituent layers are assumed to be sufficiently large so that quantum-well effects can be ignored. The material layers are characterized by frequency-dependent (macroscopic) dielectric functions. The nonradiative plasma modes are defined by the electromagnetic fields that decay exponentially away from each interface and that have an envelope that decays exponentially away from the end of the truncated superlattice. We employ a fully retarded theory in the framework of a transfer-matrix method. The general dispersion relations are shown to reproduce exactly the theoretical results for a binary semiconductor (or dielectric) superlattice. Numerical examples are presented for several illustrative cases.