Electron mobility in very low density GaN/AlGaN/GaN heterostructures

We report on the transport properties of a tunable two-dimensional electron gas (2DEG) confined at the lower interface of a GaN/Al0.06Ga0.94N/GaN heterostructure grown by plasma-assisted molecular beam epitaxy on semi-insulating GaN templates prepared by hydride vapor phase epitaxy. Using an insulated gate Hall bar structure, the electron density is continuously tuned from similar to2x10(12) down to 1.5x10(11) cm(-2). At T=300 mK, the 2DEG displays a maximum mobility of 80 000 cm(2)/V s at a sheet density of 1.75x10(12) cm(-2). At low densities, the mobility exhibits a power law dependence on density -musimilar ton(e)(alpha), with alphasimilar to1.0, over the range of 2x10(11)-1x10(12) cm(-2). In this density regime, the mobility is no longer limited by alloy scattering and long-range Coulomb scattering dominates. We discuss the dominant scattering mechanisms that presently limit low temperature mobility at electron densities below 1x10(12) cm(-2). (C) 2004 American Institute of Physics.