Experimental evidence for weak insulator-quantum hall transitions in GaN/AIGaN two-dimensional electron systems

We report comparative magnetoresistance measurements of the two-dimensional electron gas formed in two different GaN/AlGaN quantum well structures with different starting disorder. The longitudinal magnetoresistance measurements for both the samples exhibited temperatureindependent crossing points, evidence for a weak insulator - quantum Hall transition. Our data suggest that the onset of Landau quantization does not correspond to the crossing point. Moreover, the effect of the electron-electron interaction must be taken into account because the Hall resistivity shows a strong temperature dependence in the more disordered sample. Our experimental results, therefore, urge further studies on the low-field weak insulator - quantum Hall transition.