Studies of high field transport in GaN/AlGaN heterostructures

Experimental studies have been performed on the velocity-field characteristic of AlGaN/GaN heterostructures. A pulsed voltage input (with a 10 ns pulse width) in combination with a four-point measurement was used in a 50 Ω environment to determine the drift velocity of electrons in the two-dimensional electron gas as a function of the applied electric field. These measurements show an apparent saturation velocity near 3.1 × 10⁷ cm/s, at a field of 140 kV/cm. A comparison of these studies shows that the experimental velocities are close to previously published simulations based upon Monte Carlo techniques. Local inhomogeneities in the electric field are discussed as possible mechanisms for the slightly lower value of the velocity as compared to the simulation.