Intrasubband plasmons and optical transmission in random-layer-thickness n-i-p-i semiconductor superlattices.

Abstract

We investigate theoretically the intrasubband collective plasmon modes and the optical transmission in a specially constructed semiconductor superlattice consisting of n- and p-type doped semiconductors separated by an undoped intrinsic (i) semiconductor. The thicknesses of the constituent layers are randomly distributed in accordance with a designed probability, and all of them are assumed to be sufficiently large so that the quantum-size effect can be ignored. The materials of the layers are characterized by frequency-dependent dielectric functions. The discontinuity at the interfaces is dealt with by using the transfer-matrix method. The calculation of dispersion relation and optical transmission shows that in varying the degree of thickness randomness, the frequencies of the plasmon modes only exhibit small shifts, but the transmission coefficients are changed. A particular random structure is found in which some modes of electromagnetic waves with special frequencies are completely unscattered by the randomness, whereas the other modes rapidly decay. This provides a possibility of building a high-quality optical filter.