Fabrication of high-quality one- and two-dimensional electron gases in undoped GaAs/AlGaAs heterostructures

We have developed a technique for the fabrication of high-mobility electron gases formed in undoped GaAs/AlGaAs heterostructures. The use of an insula ted gate allows independent control over the carrier density in the Hall ba r and ohmic contact regions of the device. This unique design eliminates di fficulties in obtaining reliable ohmic contacts, particularly in the low ca rrier density regime. In the absence of remote ionized impurity scattering, extremely high transport mobilities are obtained at low carrier densities (1 x 10(6) cm(2) V-1 s(-1) at 1 x 10(10) cm(-2)). This design has been adap ted to the formation of undoped one-dimensional electron gases that show cl ean and reproducible conductance plateau at 1.5 K. (C) 1999 American Instit ute of Physics. [S0003-6951(99)2216-0].