HELICONS IN n-TYPE SILICON AND GERMANIUM

Abstract

Using the self-consistent field method, the collective modes of the electrons in n-type silicon and germanium in a constant external magnetic field are calculated from the frequency- and wavelength-dependent conductivity tensor σ(ω, q) for simple symmetry directions. Because of the differing orientations of the longitudinal axes of the energy surfaces relative to the direction of the external field, there is, in general, more than one carrier involved, with the result that the helicon spectrum can have more than one branch. The minimum frequencies of the higher ("optical") branches depend on the effective mass parameters in a different way than do the cyclotron resonance frequencies. The frequency spectra of all collective modes are discussed in the long-wavelength limit.