Anisotropic diffusion of In adatoms on pseudomorphicInxGa1−xAsfilms: First-p

Abstract

In the Stranski-Krastanow growth of strained pseudomorphic films, material transport by surface diffusion plays a crucial role for the development of the three-dimensional island morphology. In an attempt to elucidate the atomistic aspects of this growth mode, we study diffusion of a single indium adatom on (1ϫ3)-and (2 ϫ3)-reconstructed subcritical In 2/3 Ga 1/3 As(001) films using first-principles total energy calculations of the corresponding adiabatic potential-energy surfaces ͑PES͒. We find that In diffusion is anisotropic, and substantially enhanced compared to the conventional GaAs͑001͒-c(4ϫ4) substrate. Special attention is also paid to the methodology of deriving the tracer diffusion coefficients of indium from knowledge of the PES, using the continuous-time random-walk formalism.

Atomic processes in molecular beam epitaxy on strained InAs(137): A density-functional theory study

“…Hence we conclude that breaking the surface As dimer bond is not the process that initiates epitaxial growth on InAs͑137͒, in contrast to the case of Ga/GaAs͑001͒, where the corresponding M D is lower than the on-surface binding energies. This finding is in line with previous computational results from our group demonstrating that the broken surface As dimer bond of the GaAs͑001͒ c͑4 ϫ 4͒ surface 20 or of the In 2/3 Ga 1/3 As͑001͒ ͑2 ϫ 3͒ wetting layer 21 is energetically less favorable for indium than the corresponding on-surface sites. Only on an InAs wetting layer of 1.75 ML thickness on GaAs͑001͒, displaying the ␤2͑2 ϫ 4͒ reconstruction, recent calculations 22 find an energetic preference of In to insert into the As dimers in the trench of this reconstruction.…”

“…We call this second pathway "sideways" diffusion, again in analogy to diffusion on the ͑inclined͒ side facets of a QD. The values of the maximum energy barriers along either pathway ͑0.26 and 0.29 eV, respectively͒ are comparable to those calculated earlier for In diffusion on an In 2/3 Ga 1/3 As wetting layer on GaAs͑001͒ with ͑2 ϫ 3͒ reconstruction 21 and somewhat lower than the barriers reported for In diffusion on InAs͑001͒ in the ␤2͑2 ϫ 4͒ reconstruction 23 and In diffusion on the ␤2͑2 ϫ 4͒ reconstructed wetting layer ͑1.75 ML InAs͒ on GaAs͑001͒. 22,24 We note that the energy barriers for "uphill" diffusion and "sideways" diffusion are of comparable size, i.e., long-range diffusion on the unstrained InAs͑137͒ surface is nearly isotropic.…”

Dynamics of Ti, N, and TiNx(x=1–3) admolecule transport on TiN(001) surfaces

“…We note that selfdiffusion via double jumps has been observed experimentally for single metal adatoms on low-index metallic surfaces 50,51 and In long jumps on InGaAs(001) are predicted by DFT calculations. 52 Ti adatom migration along 110 directions is the least-frequent event observed, accounting for just 1% of the total migration distance. Ti atoms are the only adspecies for which each migration event, irrespective of the migration pathway, is a translation leading to net GC diffusion on TiN(001).…”

Adsorption of indium on an InAs wetting layer deposited on the GaAs(001) surface

“…In sec. IV we will compare our results with results [10,12,16] where this effect was instead overestimated.…”

“…For this kind of calculations both LDA [2,16,17,18,19] and GGA [10,12,20,21,22] have been used in the literature. It has been demonstrated [23,24] that both methods give qualitatively the same picture for the description of adatom adsorption on a surface, although LDA usually gives larger values for binding energies than GGA [25].…”