Phase diagram for the quantum Hall effect in a high-mobility AlGaN/GaN heterostructure

Abstract

The magnetoresistance behaviour of a high-mobility AlGaN/GaN heterostructure has been studied at low temperatures under magnetic fields of up to 28 T. Clear dissipationless minima in the Shubnikov-de Haas curves, for both cyclotron-split and spin-split Landau levels, have been observed. The temperature dependence of the widths of these minima have enabled a phase diagram for breakdown of the integer quantum Hall effect to be partially mapped out, and compared with similar results obtained for AlGaAs/GaAs heterojunctions. A distinctive feature of this sample is the variation of low-field electron mobility between different voltage probes, and corresponding differences in the quantum Hall breakdown behaviour are seen.