Abstract
High electron mobility field effect transistors were fabricated on AlGaN/GaN heterostructures and their magnetoresistance was measured at 4.2 K up to 10 T with simultaneous modulation of the gate potential. Low and high magnetic field data were used to determine the electron mobility (mu) and concentration (n), respectively, in the gated part of the transistor channel. With these measurements we present a method to determine mu and n under the gate of a transistor, which does not require knowledge of the transistor gate length, access resistance, threshold voltage, or capacitance. We discuss applications of this method for nanometer and ballistic transistors. (c) 2006 American Institute of Physics.