Pressure‐induced transition of 2DEG in δ‐doped GaAs to insulating state

The tunnelling and lateral conductance of a two-dimensional electron gas (2DEG) formed in GaAs with a 8-doped layer were measured simultaneously at hydrostatic pressures at helium temperatures. The resistivity of the δ-doped layer sharply increases by more than three orders of magnitude at about 2 GPa and its temperature coefficient changes from about -0.04 to about -4 K -1 . The tunnelling resistance shows only a slight change of exponential behaviour at about 1.5 GPa while a drastic change of the zero bias anomaly (ZBA) takes place just at the metal-insulator transition (MIT). Such behaviour is interpreted in terms of the pressure dependence of the GaAs band structure and DX-level position as well as Coulomb gap formation at the MIT.