Theory of Sb-induced triple-period ordering in GaInP - art. no. 201322

During organo-metallic vapor phase epitaxy (OMVPE) of GaInP (001) layers, t he structure of the growth surface has a profound influence on the microstr ucture, and the optical and electrical properties of the resulting bulk mat erial. The beta2 (2 x 4) surface, terminated with P dimers, provides a ther modynamic driving force for CuPtB ordering. Recently, surfactants such as S b have been used to reduce this driving force. The use of surfactants to co ntrol the surface structure during growth has allowed for band-gap tailorin g and the fabrication of heterostructures with no change in solid compositi on across the interface. Another exciting discovery was that high coverages of Sb induced a bulk triple period ordering. To further our understanding of these phenomena, the P terminated GaP(001) surface was studied via first principles calculations based on the Kohn-Sham density functional theory w ithin the local density approximation (LDA). It was determined that under i ncreasingly P-rich conditions, the beta2(2x4) and then the c(4x4) reconstru ctions are stable. When the surface is covered with Sb, several different r econstructions are found to be stable in the allowable range of chemical po tentials. Under lower group-V coverages the beta2 (2x4) is stable, while at high Sb coverage, (4x3) and (2x3) reconstructions are stable. We propose t hat these (x3) reconstructions explain the triple period ordering seen in G aInP grown with Sb as a surfactant. Total-energy calculations confirm that (x3) reconstructions provide a thermodynamic driving force for A-variant tr iple period ordering.