Electron Cyclotron Resonance in CdS

Abstract

Electron cyclotron resonance has been observed in single-crystal CdS platelets at temperatures below 4.2\ifmmode^\circ\else\textdegree\fi{}K. The single resonance seen in all orientations is consistent with a single-ellipsoid conduction-band model for CdS. The cyclotron effective masses measured with the crystal $c$ axis parallel and perpendicular to the magnetic field are $\frac{{{m}^{*}}_{c\mathrm{II}B}}{{m}_{o}}=0.171$ and $\frac{{{m}^{*}}_{c\ensuremath{\perp}B}}{{m}_{o}}=0.162$, implying that the constant-energy surfaces near the conduction-band minimum are oblate spheroids having transverse and longitudinal effective masses $\frac{{{m}_{t}}^{*}}{{m}_{o}}=0.171$ and $\frac{{{m}_{l}}^{*}}{{m}_{o}}=0.153$. The effective mass values determined from cyclotron resonance are 15% lower than those measured in other experiments. The difference cannot be due to depolarization or optical polaron effects, but can be accounted for in terms of an electron self-energy correction resulting from the piezoelectric electron-phonon interaction in CdS. Electron collision times of order ${10}^{\ensuremath{-}11}$ sec were calculated from the 70-Gc/sec cyclotron resonance data taken between 1.25 and 4.2\ifmmode^\circ\else\textdegree\fi{}K. The magnitude and temperature dependence of the collision times are best described by the theoretical predictions for piezoelectric scattering along with possibly a small neutral-impurity scattering contribution.