Frequency dependence of cyclotron resonance in si inversion layers in the region of activated conductivity

Cyclotron resonance of electrons in a Si MOSFET has been studied at a number of far infrared laser frequencies and at surface electron densities down to 3 × 10 cm^?2 in the activated conductivity regime. The scattering rate exhibits $\text{B}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ behavior for ωτ > 2 as in the metallic regime. Effective masses obtained from the fits are found to increase with decreasing density at frequencies $\text{V}\text{?}\text{? 25}\text{cm}{}^{\mathrm{?1}}$. It is possible that this continued evidence of metallic-like behavior is due to the fact that the photon energy is larger than the DC activation energy at these densities.