  The voltage-spectral density SV(f) of the 2-dimensional electron gas formed
at the interface of LaAlO3 /SrTiO3 has been thoroughly investigated. The
low-frequency component has a clear 1/f behavior with a quadratic bias current
dependence, attributed to resistance fluctuations. However, its temperature
dependence is inconsistent with the classical Hooge model, based on
carrier-mobility fluctuations. The experimental results are, instead, explained
in terms of carrier-number fluctuations, due to an excitation-trapping
mechanism of the 2-dimensional electron gas.
