The PI will set up a multi-probe experimental approach to the study of the metal-semiconductor interface formation in GaAs (100) and other III-V compound semiconductors, with the goal of simultaneously determining structural (both electronic and morphoogical) and electrical transport properties of the interface under study. In this way it will be possible to correlate the information about the Schottky barrier obtained by the local probes (photoelectron spectroscopy with synchrotron radiation) with that obtained by macroscopic probes (I-V and C-V measurements) in situ, without disturbing the sample. Such data will be of crucial importance in evaluating which of the theories put forward recently best describes the Schottky barrier, both during its formation and in the final stages of the extended interface. Also, they will have a direct relevance in the technology of GaAs processing by clarifying which of the interface structural parameters has a direct and verifiable influence on the device performances, i.e., on its transport properties.