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gallium arsenide; surface states; ab initio calculations; III-V semiconductors; semiconductor epitaxial layers; molecular beam epitaxial growth; semiconductor growth; annealing; surface morphology; surface reconstruction; surface energy; low energy electron diffraction; scanning tunnelling microscopy
Abstract:
GaAs(114)A surfaces were prepared using molecular beam epitaxy followed by annealing in As-2 pressure as well as in ultrahigh vacuum. Based on low-energy electron diffraction, in situ scanning tunneling microscopy measurements, and ab initio first-principles electronic-structure calculations the surface reconstructions are determined. Under As-rich conditions GaAs(114)A develops a beta2(2x1) and/or beta2c(2x2) reconstruction which is analogous to the GaAs(001)beta2(2x4) one. Although a low surface free energy (46 meV/Angstrom(2) for As-rich conditions) is found for GaAs(114)Abeta2(2x1), it is split up into mesoscopic (113) and (115) facets. Also typical steps between 150 A wide terraces are observed along [1 (1) over bar0]. The stoichiometric GaAs(114)A surface is mesoscopically very flat and develops a alpha2(2x1) reconstruction of a low surface free energy of 53 meV/Angstrom(2). The surface free energies for the alpha(2x1) and a newly introduced omega(2x1) variant are larger.
