Magnetotransport measurements on an AlGaN/GaN two-dimensional electron system

Abstract

We report on the transport properties of an AlGaN/GaN two-dimensional electron system in the presence of a perpendicular magnetic field B. At low magnetic fields, the measured longitudinal resistivity rho(xx) shows a B-2 dependence at various temperatures. This effect can be ascribed to electron-electron interaction effects in a weakly disordered electron system. At high magnetic fields, there is a temperature-independent point in rho(xx) at the critical magnetic field B-c. We find that at this crossing point, the Hall-resistivity rho(xy) is approximately equal to rho(xx). By analyzing the amplitude of the observed Shubnikov-de Hass oscillations at high fields, we find that at the crossing point, mu B-q = 0.17 < 1, where mu(q) is the quantum mobility. Within the Drude-Boltzman theory, mu(q) should be approximately equal to mu. The fact that mu(q) < mu could be due to a high-field localization effect which gives rise to the formation of a quantum Hall liquid-like state because p., increases with increasing temperature for B > B-c.