Journal of the Korean Physical Society, Vol. 61, No. 1, July 2012, pp. 85∼88 First-principles Studies of AlSb, GaSb, and InSb on Si(111) and Si(100) Oleg Efimov, Geunjung Lee and Young-Gui Yoon * Department of Physics, Chung-Ang University, Seoul 156-756, Korea (Received 2 May 2012) We study the energetics and the atomic structures of MSb, where M is Al, Ga, or In, monolayers or thicker layers on Si(111)1×1 substrates and Si(100)2×1 substrates from first-principles. The calculated surface energies of MSb on Si(111) differ less than those of MAs on Si(111), for each M. Si(100)2×1:Sb is the most stable for each M among Si(100)2×1, Si(100)2×1:Sb, Si(100)2×1:(MSb), and Si(100)2×1:M. The relative surface energies of thicker epitaxial overlayer films on Si(100) are larger. PACS numbers: 68.35.-p, 68.35.Bs, 68.35.Md Keywords: AlSb, GaSb, InSb, Si(111), Si(100), Energetics DOI: 10.3938/jkps.61.85 I. INTRODUCTION Research on GaSb, AlSb, and InSb is becoming popu- lar because of their potential applications in the semicon- ductor industry. GaSb, AlSb, and InSb on Si substrates may be used for band gap engineering and nanostruc- ture fabrications. Recently, epitaxial growths of GaSb [1, 2], AlSb [3, 4], and InSb [5, 6] on Si(111) substrates and Si(100) substrates have been investigated. There- fore, theoretical studies on these materials are very de- sirable. In this research, we studied the energetics of MSb (M = Al, Ga, and In) monolayers or thicker layers on Si substrates. We calculated the total energies, the atomic structures, and the surface energies of SbMSb and MSbSiSb terminated Si(111)1×1 substrates and MSb on Si(100)2×1 substrates from first-principles, and we com- pared our results with previous theoretical calculations involving As instead of Sb [7,8]. II. CALCULATION Centrosymmetric surface supercells are employed in our calculations. The calculations are performed using the ab-initio total-energy and molecular-dynamics pro- gram VASP (Vienna ab-initio simulation program) de- veloped at the Institute f¨ ur Materialphysic of the Univer- sitat Wien, using the projector-augmented-wave (PAW) approach [9]. The generalized gradient approximation (GGA) for the exchange-correlation energy functional is adopted [10]. The lattice constants of bulk AlSb, GaSb, * E-mail: yyoon@cau.ac.kr; Fax: +82-2-825-4988 and InSb (6.23 ˚ A, 6.22 ˚ A, and 6.64 ˚ A, respectively), cal- culated to check the computational accuracy, lie within a 3% range compared to the experimental data [11]. In addition, the cohesive energies of bulk AlSb, GaSb, and InSb (6.47 eV, 5.68 eV, and 5.32 eV, respectively) agree with previous experiments [11] to within 6%. For detailed information on the parameters for our calculations, see our previous works [7,8]. III. RESULTS AND DISCUSSION The surface energy E s is defined as E s = E - n Si µ Si(bulk) - 1 2 (n M + n Sb )µ MSb(bulk) - 1 2 (n M - n Sb )Δµ M , (1) where E is the total energy, n i is the number of atom i in the surface supercell, µ i is the chemical potential of atom i, and Δµ M = µ M - µ Sb . We neglect the entropy contri- bution to the surface energy because the contributions are expected to cancel each other out in the difference of surface energies. The surface energy is calculated by assuming that µ M + µ Sb = µ MSb(bulk) , as is done in the literature [8, 12]. Δµ M satisfies the following inequality including ΔH M , the heat of formation of MSb [13], |Δµ M - µ M(bulk) + µ Sb(bulk) | < ΔH M . (2) Si(111)1×1 substrates terminated with two different stacking sequences are shown in Figs. 1(a) – (b). The surface energies of these structures relative to that of Si(111)-Sb are listed in Table 1. For the case of GaSb, the relative surface energy of Si(111)-GaSbSiSb (the sur- face with the GaSbSiSb termination) is lower by about -85-