Résumé
The I-V characteristics of GaN/AlGaN HFET and 1/f noise at 4K have been measured in strong magnetic fields, where the electron mobility is affected by geometric magnetoresistance. The magnetic field dependence of the 1/f noise shows that the number of electrons fluctuations is the dominant mechanism of the 1/f noise and precludes the mobility fluctuations mechanism. The channel mobility extracted from the magnetoresistance data first increases with gate bias reaching the maximum value of ~(0.9-1.0) m2/Vs at the 2D electron concentration of 5x1012 cm-2. This maximum value is close to the estimated ballistic mobility limit of 1.2 m2/Vs determined by the electron transit time with the Fermi velocity.