PERCOLATION METAL-INSULATOR TRANSITIONS IN THE 2-DIMENSIONAL ELECTRON-SYSTEM OF ALGAAS GAAS HETEROSTRUCTURES/

We investigate the transport properties of insulating phases in the 2D electron system of high-mobility AlGaAs/GaAs heterostructures of Corb ino geometry at very low temperatures. We find that the nonlinear curr ent-voltage characteristics for insulating phases in the integer and f ractional quantum Hall regime and for a low-density insulating phase a re very similar. The behavior of these characteristics with changing t emperature and filling factor unambiguously points to the percolation metal-insulator transition as the cause for all insulating phases inve stigated. We propose a metal-insulator phase diagram in the (B, N-s) p lane based on our experimental data.