Raman scattering and collective excitations in doped tunneling semiconductor superlattices.

Abstract

We present a theoretical study of the electronic excitations in doped tunneling semiconductor superlattices of finite size. Raman scattering yields are obtained from the density-density response function, providing mode dispersion relations and relative intensities. We find that as the intraminiband and interminiband plasma modes carry most of the oscillator strength, other single-particle-like excitations have nonvanishing intensities as well. Strong surface-related modes, associated with charge depletion near the surface layers, are shown for finite wavelengths. The intraminiband plasma mode exhibits a two-dimensional-like behavior for long wavelengths, and carries most of the oscillator strength for short ones, while one of the surface modes shows a nearly linear dispersion relation. A novel tunneling mode has nonzero frequency and strength as the wave vector approaches zero.