Suitable system for observation of surface plasmons in a semi-infinite semiconductor superlattice

A model of a semi-infinite semiconductor superlattice topped with a metal and insulator is suggested. The dispersion relation for surface plasmons is derived. Similarly to the case of type-II and other complex unit cell superlattices, by varying the thickness of the insulator, the critical wave vector can be lowered and the frequency of the surface plasmon can be chosen for a given wave-vector value. It is interesting to notice that one branch of the surface plasmon with null critical wave vector exists below the bulk plasmon continuum, and the frequency is directly related to the ratio of the thickness of the insulator d to the superlattice spacing a.