| AVS 59th Annual International Symposium and Exhibition | |
| Surface Science | Wednesday Sessions |
| Session SS+EM-WeA |
| Session: | Semiconductor Surfaces |
| Presenter: | J.C. Thomas, University of Michigan |
| Authors: | J.C. Thomas, University of Michigan A. Van der Ven, University of Michigan N.A. Modine, Sandia National Laboratories J.M. Millunchick, University of Michigan |
| Correspondent: | Click to Email |
Increasing evidence linking bulk material properties to surface structure has made critical the development of a comprehensive understanding of atomic-scale surface structure. This is particularly true in low-temperature-grown (LTG) GaAs, where As anti-site defects are incorporated at the As-rich growth surface. Unfortunately, GaAs(001) reconstruction stability is poorly characterized in this regime, where, in addition to the well-studied β2(2×4) and c(4×4) reconstructions, a "×3" reconstruction is also observed. This "×3" reconstruction has been difficult to characterize experimentally, and theoretical calculations have failed to identify a stable "×3" reconstruction on GaAs(001). We have developed a systematic, rigorous procedure for predicting equilibrium surface structure and ordering behavior at finite temperature. By combining new and established techniques, our method overcomes difficulties of studying multicomponent surfaces from first principles, which has traditionally followed a painstaking trial-and-error approach.
Using our approach of directed structural enumeration and density functional theory calculation, we can efficiently identify stable and near-stable reconstructions of the GaAs(001) surface in order to identify the structure of the missing "×3" reconstruction. Accounting for lattice vibrations and configurational entropy from first principles, we predict finite-temperature stability of a (4×3) reconstruction over a range of As4 partial pressure at low temperature. Our results reveal a competition between vibrational entropy of the (4×3) reconstruction and configurational entropy of the c(4×4) reconstruction, which becomes entropically stabilized at higher temperatures. We find that this same (4×3) reconstruction features prominently in calculated reconstruction phase diagrams for the wetting layer systems Bi/GaAs(001) and InAs/GaAs(001).