Cyclotron resonance measurements of the non-parabolicity of the conduction bands in silicon and germanium

The non-parabolicities of the transverse effective masses mperpendicular to * for the lowest conduction band minima are measured in silicon and germanium by means of cyclotron resonance at submillimeter wavelengths. For silicon a 2+or-1% increase in mperpendicular to * at 10 meV into the band is found, whereas for germanium an 8+or-4% increase at 50 meV is measured. A recent report by Fink and Braunstein (Solid St. Commun., vol.15, p.1627 (1974)) that the cyclotron resonance scattering time in germanium decreases by up to a factor of five in going from a measuring frequency of 35 GHz to 891 GHz is shown not to occur for high-purity samples of silicon and germanium.