ISSN 0021-3640, JETP Letters, 2011, Vol. 93, No. 10, pp. 585–590. © Pleiades Publishing, Inc., 2011. Original Russian Text © O.E. Tereshchenko, D.V. Dmitriev, A.I. Toropov, S.V. Eremeev, S.E. Kulkova, 2011, published in Pis’ma v Zhurnal Eksperimental’noi i Teoreticheskoi Fiziki, 2011, Vol. 93, No. 10, pp. 647–652. 585 Surfactants improving the two-dimensional layer growth are now often added to a semiconductor grown by molecular beam epitaxy [1–3]. To implement two- dimensional growth, the entering atoms should be able to diffuse over the surface and to be incorporated into steps. If the temperature is so low that the free diffu- sion of adatoms is impossible, the growing surface usu- ally has a developed relief. The main idea in the use of surfactants is an increase in the surface diffusion coef- ficient of adatoms through a decrease in the binding energy of entering atoms of the growing layer with a substrate. A surfactant, which is a “pollution” for the bulk, should “emerge” on the surface of the growing film. The condition of the two-dimensional layer-by- layer growth is the Bauer criterion [4] (1) where σ ad and σ sub are the surface energies of the adsorbed layer and substrate, respectively, and γ i is the energy of the interface. Change in the sign in Eq. (1) leads to three-dimensional growth. The presence of a surfactant on the surface can significantly affect the states of surface atoms of the semiconductor, saturat- ing broken bonds and changing the energy of the sub- strate surface and thereby the growth conditions. The standard temperatures of the molecular beam epitaxy growth of GaAs are 580–620°C. These temperatures are much lower than the temperature of the growth of σ ad γ i σ sub – + 0 , < GaAs by almost equilibrium liquid- and gas-phase epitaxy. For this reason, layers of a similar quality in molecular beam epitaxy can be obtained owing to kinetic factors [5], in particular, a low growth rate and a sufficiently high surface diffusion coefficient at T ~ 600°C. However, at high temperatures, diffusion, seg- regation, and mixing of atoms in the growth of hetero- structures lead to the smearing of the interfaces of het- erojunctions. The interlayer mixing effect can be reduced by reducing the growth temperature. A decrease in the temperature inhibits the kinetics of the incorporation of Ga and As and thus increases the concentration of point defects. Thus, the role of the surfactant in low-temperature growth is reduced to the conservation of thermodynamic inequality (1) and the diffusion coefficient of atoms arriving at the surface in molecular beam epitaxy, which determines the kinetic constraints on the LG of the crystal. Numerous systems where the properties of surfac- tants were used have been studied: epitaxy of IV-group semiconductors [6], III–V compounds [7], and mixed systems on various substrates [1–3]. Atomic hydrogen is an efficient surfactant and makes it possible to reduce the growth temperature of GaAs(001) from 600 to 330°C without loss of the structure quality of the growing film [8]. However, the temperature range of the use of atomic hydrogen as a surfactant is only 300– 400°C and is determined by the adsorption and des- Surfactant Properties of Cesium in Molecular Beam Epitaxy of GaAs(100) O. E. Tereshchenko a, b , D. V. Dmitriev a, b , A. I. Toropov a, b , S. V. Eremeev c, d , and S. E. Kulkova c, d a Institute of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences, pr. Akademika Lavrent’eva 13, Novosibirsk, 630090 Russia e-mail: teresh@thermo.isp.nsc.ru b Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090 Russia c Institute of Strength Physics and Materials Science, Siberian Branch, Russian Academy of Sciences, Akademicheskii pr. 2/1, Tomsk, 634021 Russia d Tomsk State University, pr. Lenina 36, Tomsk, 634050 Russia Received April 5, 2011 The experimental and ab initio investigations of the effect of a decrease in the binding energy of surface arsenic atoms under the cesium adsorption on an As-stabilized GaAs(001)-(2 × 4) surface have been per- formed. The cesium-induced redistribution of the charge on the surface atoms reduces the electron density in the As–Ga bond of the upper layer of the GaAs(001) surface; thus, the As–Ga binding energy decreases and, as a result, the diffusion activation energy, as well as the arsenic atom desorption, decreases. An increase in the diffusion coefficient of surface atoms, along with the property of Cs to segregate on the surface of a growing semiconductor film, makes it possible to use cesium as a surfactant in the low-temperature growth of GaAs by molecular beam epitaxy. DOI: 10.1134/S0021364011100122