Bulk GaN and AlGaN∕GaN heterostructure drift velocity measurements and comparison to theoretical models

The room-temperature velocity-field characteristics for n-type gallium nitride and AlGaN∕GaN heterostructures, grown epitaxially on sapphire, were determined experimentally. A pulsed voltage input and four-point measurements were used on special geometry samples to determine the electron drift velocity as a function of applied electric field in the basal plane. These measurements show apparent saturation velocities near 2.5×107cm∕s at 180kV∕cm for the n-type gallium nitride and 3.1×107cm∕s at 140kV∕cm for the AlGaN∕GaN heterostructures. A comparison of these studies shows that the experimental velocities are close to previously published simulations based upon Monte Carlo techniques.