(001)-oriented GaAs surfaces were passivated using Si interface control layer (Si-ICL) formed on surfaces having Ga-rich (4×6) reconstructions. Metal-insulator-semiconductor (MIS) structures were fabricated by direct nitridation of Si-ICL to partially converting into SiN{sub}x, and further depositing a thick SiO{sub}2 layer on top as the main passivation dielectric. Reflection high-energy electron diffraction, in-situ X-ray photoelectron spectroscopy and MIS capacitance-voltage techniques were used for characterization. The initial surface reconstruction was found to have a surprisingly strong effect on the degree of Fermi level pinning at the MIS interface. In contrast to the standard As-rich (2×4) surfaces, which result in strongly pinned MIS interfaces, the novel SiO{sub}2/SiN{sub}x/Si ICL/GaAs MIS structures formed on "genuine" (4×6) surface realized complete unpinning of Fermi level over the entire band gap with a minimum interface state density of 4×10{sup}10 cm{sup}(-2)eV{sup}(-1) range. Furthermore, the passivation technique has been successfully applied to the fabrication of insulated gate FETs, realizing good gate controllability.
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