Band bending in semiconductors: chemical and physical consequences at surfaces and interfaces.

The reflectance anisotropy has been calculated by microscopic tight-binding theory for various configurations of the As-rich GaAs(100) cs4 3 4d and s2 3 4d reconstructions, based on precise atomic coordinates from ab initio total-energy minimization. The comparison to experimental reflectance anisotropy in combination with scanning tunneling microscopy and low energy electron diffraction allows one to identify precise correlations between structural units and optical features. Clear indications are obtained for the intermediate steps in the surface reconstruction transformation. [S0031-9007(98)06681-2]

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Reflectance Anisotropy of GaAs(100): Theory and Experiment

The optical anisotropy of differently reconstructed GaAs(001) surfaces has been analysed both theoretically and experimentally. The atomic structures and RAS spectra are calculated from first principles for the As-rich c(4 × 4) and β2(2 × 4) as well as for the stoichiometric α2(2 × 4) and the Ga-rich ζ(4 × 2) surface phases. These results are compared with spectra recorded at low temperature (40 K). We find good agreement between the calculated and measured data, in particular for the As-rich surface phases. In marked contrast to earlier calculations we find the peak near the E1 critical point energy, characteristic of the β2(2 × 4) surface, to originate from electronic transitions in bulk layers. The experimental data for the Ga-rich (4 × 2) surface phase are less well reproduced, possibly due to surface defects or structural deviations from the ζ(4 × 2) model for the surface geometry.

GaAs(001): Surface Structure and Optical Properties

There currently exists a wide range of powerful techniques for probing surfaces, mainly involving the use of electron or ion beams under high- or ultra-high-vacuum conditions. Recently there have been major efforts to develop surface sensitive optical probes that have the inherent advantage that they can be applied in more challenging environments such as in high pressures or under liquids and in real time. The most powerful of these techniques to emerge ( years ago) is reflection anisotropy spectroscopy (RAS), which early on demonstrated its ability to distinguish different reconstructions of GaAs(001) and to detect monolayer-growth-related oscillations similar to those routinely obtained using reflection high-energy electron diffraction. This article describes some aspects of the development of the RAS technique since that time, focusing on our own theoretical and experimental studies concerning the (001) surfaces of cubic semiconductors which have been prepared by molecular beam epitaxy. These studies demonstrate that in surface chemistry, structure and electronic properties RAS has made powerful contributions to the study of such surfaces.

Aspects of reflectance anisotropy spectroscopy from semiconductor surfaces

Surface quality and atomic structure of MBE-grown GaAs(100) prepared by the desorption of a protective arsenic layer

The influence of hydrogen adsorption on the surface order, dielectric function, and dielectric anisotropy was investigated for the three main reconstructions of the GaAs(100) surface [c(4×4), (2×4), (4×2)] by low‐energy electron diffraction, spectroscopic ellipsometry, and reflectance difference spectroscopy. For all reconstructions, low hydrogen exposure removes the surface dimers, whereas surface roughening is observed at high hydrogen exposures. However, detailed differences can be resolved depending on the surface reconstruction. On the As‐rich c(4×4) surface, the outermost As‐dimers are removed at low H‐exposures leaving behind a still As‐rich surface of (1×1) symmetry. Thereafter, more As is removed and a new surface anisotropy develops due to the exposed Ga‐dimers arranged in a mixture of (1×2) and (√2×√2)‐reconstructions. For H‐adsorption on the (2×4)‐ and (4×2)‐surfaces, in contrast, only the subsequent reduction of the surface reconstruction is observed with increasing exposure, but no structura...

Hydrogen‐induced modification of the optical properties of the GaAs(100) surface

Hydrogen induced structure changes of GaAs(100) c(4×4), (2×4) and (4×2) surfaces

Influence of hydrogen adsorption on the optical properties of the GaAs(100)-c(4×4) surface

Growth of Sb on Si(111) studied by Raman scattering

HREELS analysis of band bending on sulfur-covered GaAs(100) surfaces

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