Magnetooptics of two-dimensional electrons under the conditions of integral and fractional quantum hall effect in Si-MOSFETs and GaAs-AlGaAs single heterojunctions
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An optical spectroscopy method for the investigation of two-dimensional (2D-) electron energy spectra in the regimes of the integral and fractional Quantum Hall Effect is considered. The structure of the Landau levels is studied both in (001)-Si-Metal-Oxide-Semi-conductor Field Effect Transistors (MOSFETs) and in GaAs-AlGaAs heterojunctions. It is shown that the spectrum of radiative recombination of 2D-electrons with photoexcited holes in the case of the (001)-Si-MOSFETs directly reflects the one-particle density of states of 2D-electrons. The magnitudes of the valley and the spin splittings are determined and it is shown that these splittings are very strongly enhanced by the exchange interaction effect. Oscillations of the Landau level width as a function of the electron filling factor are observed and it is demonstrated that this effect is due to the screening of long-range random potential fluctuations.
Under the conditions of the fractional Quantum Hall Effect a splitting of the luminescence peak is observed for the first time. This splitting determines the magnitude of the chemical potential discontinuity and therefore the value of the Coulomb gap. It is found that the condensation of the 2D-electrons into an incompressible Fermi-liquid can be characterized by a critical temperature which depends on the magnitude of the Coulomb gap.
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