Independent contacts to a double-electron gas using mesoscopic surface gates

We demonstrate how two two-dimensional electron gases can be independently contacted using only surface gates defined by electron-beam lithography: ma croscopic bar gates to contact the lower layer, and mesoscopic split gates to contact the upper layer. When the technique is applied to a sample consi sting of two 150 Angstrom GaAs wells separated by 300 Angstrom Al0.33Ga0.67 As barrier, there is more than 30 M Omega isolation at 5 K for interlayer v oltages up to +/- 30 mV; the interlayer isolation operates up to 30 K. The independent contacts are used for a preliminary investigation of two parall el one-dimensional quantum wires. (C) 2000 American Institute of Physics. [ S0021-8979(00)05208-7].