Ab Initio Molecular Dynamics Simulations of Surfaces and Interfaces

摘要

This work was to develop and apply density-functional methods to semiconductorsurfaces and interfaces. The method of Linear Muffin Tin Orbitals (LMTO) was used to make a detailed study of the properties of the ideal metal/GaAs interface. This was the first systematic study of the properties of a Schottky barrier using a first-principles method, and these explicit calculations shed light on some of the many theories which have been advanced to explain its observed pinning behavior. This work was pursued further along two lines. First, some As antisite defects were incorporated in planes near the metal interface, to determine to what extent they alter the Schottky barrier pinning position. The early stages of Schottky barrier formation are also studied using the LMTO method. This work confirms the tight-binding picture that potential of the first layer of GaAs deepens as Al is deposited. We also predict the Al atom favors the Ga site over the As site; and that the reconstructed free GaAs surface partially (but not completely) dereconstructs as metal adatoms are deposited. We are hopeful that this approach will quantitatively predict donor and acceptor levels, and pinpoint the evolution of the interfacial dipole and the onset of metallization.