Probing electrical properties of molecule-controlled or plasma-nitrided GaAs surfaces: Two different tools for modifying the electrical characteristics of metal/GaAs diodes

This work shows how partial monolayer of organic molecules or radio-frequency remote plasma surface treatment affects the electrical transport across Au/n-GaAs junctions. In the first case, a series of molecules with systematically varying dipole moment were adsorbed on n-GaAs surfaces, whereas in the second case GaN ultra-thin layers with different thickness were formed by N-2-H-2 GaAs plasma nitridation, prior to contact deposition. The characteristics of electrical charge transport across the resulting interfaces were studied by current-voltage (I-V), internal photoemission (IPE), and capacitance-voltage (C-V) techniques. In this way, we find that the simplest description for the experimentally observed data is in terms of two different barrier heights, rather than one barrier height, at the interface. The first could be identified with areas free of modified GaAs, and the second with areas controlled by electrostatic effects of adjacent dipolar domains, which affects also semiconductor regions under the film's pinholes. (c) 2006 Published by Elsevier B.V.