We present a comparative study, at 300 K and at low longitudinal field, of the DC characteristics and the low-frequency noise in the drain current of GaAs/AlGaAs MODFETs which, ideally, differ only by the doping mode of the AlGaAs layer. The higher 1/f-like noise in the δ-doped structure is consistent with our previous suggestion that charge fluctuations under the gate contribute significantly to the 1/f-like noise. This work further indicates that the charge centers are related to the Si dopants under the gate.