  The line shape of the Shubnikov-de Haas (SdH) oscillation has been analyzed
in detail for a GaAs/AlGaAs two-dimensional electron gas. The line shape, or
equivalently the behavior of the Fourier components, of the experimentally
observed SdH oscillation is well reproduced by the sinusoidal density of states
at the Fermi energy that oscillates with a magnetic field in a saw-tooth shape
to keep the electron density constant. This suggests that the broadening of
each Landau level by disorder is better described by a Gaussian than by a
Lorentzian.
