INVESTIGATION OF THE CURRENT INJECTION PROPERTIES OF OHMIC SPIKES IN NANOSTRUCTURES

We investigate the mechanism by which annealed Ni-Au-Ge metallizations establish electrical contact to the two-dimensional electron gas (2DE G) in AlGaAs/GaAs heterostructures and we assess the suitability of th is contact process fbr defining patterned contacts in semiconductor na nostructures. We present a picture where electrons are injected from a n array of spikes which extend below the surface-metal pattern to pene trate the 2DEG and the associated quantum waves determine the contact resistance through phase-coherent interference processes at low temper atures. To probe this mesoscopic current injection process, we induce an evolution between two distinct geometries traditionally used to cha racterize semiconductor systems-the Corbino disc and the Hall bar. We also discuss refinements to the injection process which will facilitat e the incorporation of shaped ohmic contacts into future nanostructure designs. (C) 1998 Academic Press.