From localization to Landau quantization in a two-dimensional GaAs electron system containing self-assembled InAs quantum dots

We have studied insulator--quantum Hall--insulator (I-QH-I) transitions in a gated two-dimensional GaAs electron gas containing InAs quantum dots. In this system Shubnikov--de Haas oscillations are observed in both the low-field and high-field insulating regimes, showing that Landau quantization and localization can coexist. A phase diagram is constructed based on our experimental results, and we see that the critical points of the I-QH-I transitions do not correspond to crossover from localization to Landau quantization. Moreover, good scaling behavior is observed on both sides of low- and high-field I-QH transitions.