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The formation of a two-dimensional ͑2D͒ electron channel at semiconductor surfaces has been studied by high-luminosity and high energy-resolution ultraviolet photoelectron spectroscopy. A large variety of bandbending sources ͑alkali metals, silver and antimony adatoms, cleavage defects͒ on different narrow-gap III-V͑110͒ substrates ͑InAs, InSb͒ has been used. The measured photoemission spectral density in the semiconductor conduction band shows a steplike structure, consistent with the description of a jelliumlike 2D electron gas confined in a potential well, and it is independent of the band-bending sources. A self-consistent solution of the Poisson and Schrödinger equations gives the energy eigenvalues, the eigenstates, and the spectral density, in excellent agreement with the collection of photoemission results. Moreover, the accumulated charge density ranges between 3ϫ10 11 and 2ϫ10 12 electrons/cm 2 , consistent with previous experimental results on plasmon excitations.

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This paper studies the dependence on the silicon film thickness (TsI) of the electron mobility in Single-(SG) and Double-Gate (DG) Ultra-Thin (UT) SO1 MOSFETs. A comprehensive model was developed, including acoustic and, optical phonon scattering and the scattering with possible interface states and microscopic roughness at both interfaces. The Tsr dependence of the effective mobility ( p e f f ) predicted by simulations is, at moderate inversion densities (N,,,), weaker than what observed in experiments. We analyze the physical origin of this discrepancy, with particular attention to the phonon limited mobility. Our results indicate that scattering with surface optical phonons is strongly enhanced in UT silicon layers and that it may help explain the experimental behavior of p e f f .