Cyclotron effective mass in wide parabolic quantum wells

This is the authors' abstract. We don't add key points for this paper.

Cyclotron-resonance measurements are reported for wide (100--300 nm) modulation-doped Alₓ{Ga}_{1{{-}}x}$As graded parabolic quantum wells for electron areal densities ${N}S$=${10}⁹$/${cm}²--2.5×{10}¹¹$/${cm}²$. A clear dependence of the cyclotron frequency on ${N}S$ is observed in the extreme quantum limit which is understood in terms of alloy effects. Self-consistent calculations that include the x dependence of the local effective mass and exchange-correlation effects in a local-density approximation are in quantitative agreement with the measurements for high densities. At low densities a pinning of the cyclotron frequency is observed that is not predicted by the model.