| AVS 55th International Symposium & Exhibition | |
| Surface Science | Friday Sessions |
| Session SS+EM+NC-FrM |
| Session: | Semiconductor Surfaces |
| Presenter: | M.H. Mignogna, The Pennsylvania State University |
| Authors: | M.H. Mignogna, The Pennsylvania State University K.A. Fichthorn, The Pennsylvania State University |
| Correspondent: | Click to Email |
The GaAs (001) β2(2x4) reconstruction is the most commonly used substrate for growth in GaAs homoepitaxy by molecular beam epitaxy. Kinetic Monte Carlo (KMC) simulations based on first-principles calculations1 have illuminated the mechanisms for recovering this reconstruction during growth. However, the KMC simulations are based on rates of processes that occur on perfect β2(2x4) unit cells. In experimental studies with reflection high-energy electron diffraction and scanning-tunneling microscopy, the surface is observed to exhibit domains of perfect β2(2x4) unit cells, but long-range disorder persists and a possible origin is out-of-phase β2(2x4) domains.2 To examine the atomic-scale processes that lead to long-range disorder, as well as to characterize diffusion and the early stages of homoepitaxy on this surface, we employ accelerated molecular dynamics (MD). Our simulations are based on a semi-empirical, Tersoff-type potential that exhibits good agreement with a variety of bulk and surface properties of GaAs. Using accelerated MD we can probe long time scales, extending into the microsecond range and beyond. On the bare surface, we observe breaking, re-forming, and shifting of As row and trench dimers, that promotes the formation of out-of-phase domains of β2(2x4) unit cells and leads to long-range disorder of the surface. The kinetic processes of the As dimers affect the surface diffusion of Ga adatoms, as well as the initial morphologies that occur during growth.
1 P. Kratzer, E. Penev, M. Scheffler, Appl. Phys. A 75, 79 (2002)
2 D.W. Pashley, J.H. Neave, B.A. Joyce, Surf. Sci., 582, 189 (2005).