  We present a systematic characterization of fluctuations in submicron Hall
devices based on GaAs/AlGaAs two-dimensional electron gas heterostructures at
temperatures between 1.5 K to 60 K. A large variety of noise spectra, from 1/f
to Lorentzian, are obtained by gating the Hall devices. The noise level can be
reduced by up to several orders of magnitude with a moderate gate voltage of
0.2 V, whereas the carrier density increases less than 60% in the same range.
The significant dependence of the Hall noise spectra on temperature and gate
voltage is explained in terms of the switching processes related to impurities
in n-AlGaAs.
