First-principles studies of kinetics in epitaxial growth of III-V semiconductors

Abstract

We demonstrate how first-principles calculations using density-functional theory (DFT) can be applied to gain insight into the molecular processes that rule the physics of materials processing. Specifically, we study the molecular beam epitaxy (MBE) of arsenic compound semiconductors. For homoepitaxy of GaAs on GaAs(001), a growth model is presented that builds on results of DFT calculations for molecular processes on the β2-reconstructed GaAs(001) surface, including adsorption, desorption, surface diffusion and nucleation. Kinetic Monte Carlo simulations on the basis of the calculated energetics enable us to model MBE growth of GaAs from beams of Ga and As2 in atomistic detail. The simulations show that island nucleation is controlled by the reaction of As2 molecules with Ga adatoms on the surface. The analysis reveals that the scaling laws of standard nucleation theory for the island density as a function of growth temperature are not applicable to GaAs epitaxy. We also discuss heteroepitaxy of InAs on GaAs(001), and report first-principles DFT calculations for In diffusion on the strained GaAs substrate. In particular we address the effect of heteroepitaxial strain on the growth kinetics of coherently strained InAs islands. The strain field around an island is found to cause a slowing-down of material transport from the substrate towards the island and thus helps to achieve more homogeneous island sizes.

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

“…As a first step in this direction, some of us have previously investigated the effect of strain on In diffusion on the GaAs͑001͒-c(4ϫ4) surface. 19,20 The latter reconstruction is present on the GaAs substrate when depositing under As-rich conditions. 21,22 The next challenging question concerns the In diffusivity on the WL before the critical thickness is reached, i.e., for Ͻ c .…”

Kinetic Monte Carlo simulation of the nitridation of the GaAs (100) surfaces

“…The energies involved in the nitridation process are relatively higher if we compare to those of the GaAs homoepitaxy, which have values at the order of 2 eV of magnitude [8,14]. During the nitridation, other processes, such as diffusion of N over the surface, also takes place.…”

“…8 and 14. For this preliminary simulation, we have considered only the processes (and their respective energies) of the N adsorption at site C, as well the N diffusion along the paths [-1 1 0] and [1 1 0] [16], with a common prefactor of 10 13 s −1 [8]. We have done, so, two simulations: in the first one, we have varied the N coverage form 0.01 ML to 0.5 ML, at a fixed N flux of 0.15 ML/s, and at 700 K of growth temperature and, in the second, we have varied the N flux at three growth temperatures, 600, 700 and 800 K, keeping fixed the coverage at 0.5 ML.…”

“…In order to understand the physical mechanisms for IIInitride growth in the zinc-blende structure, we present, in this work, our preliminary results from a theoretical study of the adsorption of N over As-rich GaAs (100) (2×1) surfaces, based both on accurate, parameter-free, selfconsistent total energy and force calculations using the density functional theory, the local-density approximation for the exchange-correlation term, within the plane-wave pseudopotential method (ABINIT code [7]), together with a kinetic Monte Carlo simulation of the epitaxial growth, based on the solid-on-solid approach [8]. We have used the TroullierMartins pseudopotentials [9], and we have included Ga-3d electrons as valence states.…”

Ab initiothermodynamics of deposition growth: Surface terminations of TiC(111) and TiN(111) grown by chemical vapor deposition

“…It also provides predictive power and thus an opportunity to accelerate innovation. 13 Coupling DFT to either thermodynamic [14][15][16][17][18] or kinetic modeling [19][20][21][22] has proven extremely useful for interpreting and complementing experimental techniques in characterization of surfaces, 23 thin films, 24 and interfaces. 25 Such modeling is often well-suited for descriptions of structures that are fabricated or investigated under well-controlled conditions, such as ultra-high vacuum (UHV) or molecular beam epitaxy 26 (MBE).…”