GAAS (111) AND 1BAR1BAR1BAR SURFACES AND THE GAAS/ALAS (111) HETEROJUNCTION STUDIED USING A LOCAL ENERGY DENSITY

We use a local energy density E(r) within density-functional theory to study GaAs (111) and (111BARBARBAR) surfaces, and the GaAs/AlAs (111) heterojunction. We use E(r) to calculate the formation enthalpy of a single isolated GaAs (111) and (111BARBARBAR) surface, which is not possible with the use of conventional total-energy methods. We are able to address questions related to the stability of these surfaces. Our methods also apply to heterojunctions where we consider GaAs/AlAs (111) as a prototype. We use E(r) to calculate the formation enthalpy of the Ga-rich and Al-rich interfaces, which are distinct and which are both inherent in the supercell geometry.