Pinning-free GaAs MIS structures with Si interface control layers formed on (4 × 6) reconstructed (0 0 1) surface

(0 0 1)-Oriented GaAs metal–insulator–semiconductor (MIS) structures having a silicon interface control layer (Si ICL) were fabricated on surfaces having Ga-rich (4×6) reconstructions. Si ICL was grown by molecular beam epitaxy. MIS structures were fabricated by partially converting Si ICL to SiNx by direct nitridation, and further depositing a thick SiO2 layer on top as the main passivation dielectric by plasma-assisted chemical vapor deposition. Reflection high-energy electron diffraction, in situ X-ray photoelectron spectroscopy and MIS capacitance–voltage (C–V) 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) surface, which results in strongly pinned MIS interfaces, the novel SiO2/SiNx/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 4×1010 cm−2 eV−1 range.