Space-charge layers on Ge surfaces. II. High-frequency conductivity and cyclotron resonance

Abstract

We examine the high-frequency conductivity and cyclotron resonance of electrons in a space-charge layer on a Ge (111) surface. It is shown from the frequency dependence of the infrared absorption that the surface carriers are localized or at least strongly perturbed for densities ${N}_{s}\ensuremath{\lesssim}1\ifmmode\times\else\texttimes\fi{}{10}^{12}$ ${\mathrm{cm}}^{\ensuremath{-}2}$. The cyclotron resonance shows a shift of the resonance to low magnetic field at such densities. Only above \ensuremath{\sim}2 \ifmmode\times\else\texttimes\fi{} ${10}^{12}$ ${\mathrm{cm}}^{\ensuremath{-}2}$ is the free-electron cyclotron mass observed.