Journal of Crystal Growth 236 (2002) 511–515 Role of As 2 molecules on Ga-terminated GaAs(001) surfaces during the MBE growth Akira Ishii*, Kaori Seino 1 , Tsuyoshi Aisaka Department of Applied Mathematics and Physics, Tottori University, 4-101, Minami, Koyama, Tottori 680-8552, Japan Received 26 November 2001; accepted 2 December 2001 Communicated by M. Uwaha Abstract The first-principle calculations for the processes of migration and dissociation for an As 2 molecule on GaAs(001) surfaces is performed. The calculation of the migration for paired As atoms on top-layer Ga dimers at Ga-terminated GaAs(001)-b2ð4  2Þ surface shows us that As atoms form As 2 ad-dimer at the interspace between the dimer rows, and, by forming As 2 molecule, As atoms have extra stable sites almost on the Ga atoms. r 2002 Published by Elsevier Science B.V. PACS: 81.10.h; 81.10.Aj Keywords: A1. Crystal structure; A3. Molecular beam epitaxy; B1. Gallium compounds; B2. Semiconducting gallium arsenide 1. Introduction The investigation on the molecular beam epitaxial (MBE) growth of GaAs(001) has been studied as a typical example of compound semiconductor growth. The island growth and the step flow during growth have been reproduced computationally with the kinetic Monte Carlo technique [1–8] and the migration of each atom has been investigated using the first-principle calculations [9–14]. Recently, it has been revealed that the growth mode and surface morphology are largely dominated by the kinetics of As atoms rather than that of Ga during the epitaxial growth of a vicinal GaAs(001) surface [4–8]. This result implies the importance of the kinetics of As adatoms as well as that of Ga adatoms. Thus, in order to reproduce the growth of GaAs(001) surface, we should know at least the migration of Ga atom on the As terminated surface area and that of As atom on the Ga terminated surface area. The understandings of the mechanism of As adatom on GaAs surface during MBE are also required as well as that of Ga adatom. The migration for single arsenic adatom on Ga- terminated GaAs(001) surface during MBE growth has been studied previously using the first-principle total-energy calculations in previous papers [15,16]. The anisotropic migration of an As adatom was shown to be qualitatively similar to a *Corresponding author. Tel.: +81-857-31-5630; fax:+81- 857-31-5630. E-mail address: ishii@damp.tottori-u.ac.jp (A. Ishii). 1 Present address: Institut fur Festkorpertheorie und Theore- tische Optik, Friedrich-Schiller-Universit . at, Max-Wien-Platz 1, 07743 Jena, Germany. 0022-0248/02/$-see front matter r 2002 Published by Elsevier Science B.V. PII:S0022-0248(01)02226-6