Controlled Carrier Depletion around Nano-Scale Metal Discs Embedded in GaAs

Matrices of uncontacted, nano-scale, tungsten discs, embedded in GaAs by epitaxial overgrowth, have been characterised electrically. By varying the spacing between the discs, it is demonstrated that when the disc separation is smaller than 300 nm (for a doping level of 1016 cm-3), the conductance drops by seven orders of magnitude and the material becomes semi-insulating. The presence of the metal-induced barrier is deduced from the temperature dependence of the current transport. These results are discussed in terms of overlapping Schottky depletion regions around the discs.