Abstract
Layers of semi-insulating GaAs have been realised by epitaxial overgrowth over matrices of nm-sized tungsten discs. By fabricating and characterising structures with different metal disc densities, the influence of metal-induced carrier depletion on the resistivity in GaAs is demonstrated. The vertical current transport in this material shows a distinct decrease as the metal discs are spaced closer than 400 nm, which indicates an onset of overlapping Schottky depletion regions. From the temperature dependence of the current transport at different bias conditions, we deduce the height of the internal barriers, which are built-up in the semiconductor material between the discs, and their variation with the applied voltage. Finally, the actual metal–semiconductor Schottky barrier height is obtained from the spectral distribution of a photoresponse, which we attribute to electron excitation in the buried discs in the otherwise semi-insulating GaAs layer.
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