Atomistic Modeling, reconstructions and surface facets of GaAs(112)B surface: structural and electronic properties by ab initio calculations

Παύλος Δαμιανού Μουρατίδης
The purpose of this study is the construction and analysis of GaAs (112)B surface as well as the growth mode of InAs QD's on this surface. The theoretical model predicts that the surface (112)B of GaAs is unstable and consists of the more stable {(111)B, (101), (011), (113)B or (123)B, (124)B, (214)B} surfaces with two possible shapes of pyramidal structure. The computational simulations of surfaces for the lattice constants, recon- structions, band structures and density of states, are
more » ... ed with the ab initio AIMPRO package using the LDA Hurtwigsen-Goedecker-Hutter pseudopotentials and Gaussian orbitals as its wavefunctions basis sets. The aim is the reconstruction and relaxation of the surfaces and not the bulk material, so we need to add a vacuum in the vertical direction of the surfaces. The structures of those surfaces emerge to be all orthorhombic with the surface on the top of the orthorhombic box. So if we want to run the slab mode of AIMPRO we need to discharge the bottom surface of the orthorhombic box and wipe out all the dangling bonds which will be the cause of interaction between the top and the bottom side of the box. An exception is the case where the top and bottom side of the box are completely symmetric. The well-established method that we followed is to use pseudohydrogen atoms with a fractional charge H1.25 and H0.75 in order to saturate both Ga and As dangling bonds respectively. It is known that the group-III cation that in our case is Ga atom contributes 3/4e- to a covalent bond with the As atom, so each dangling bond needs a H1.25 pseudo-hydrogen. On the contrary the group-V anion that in our case is As atom contributes 5/4e- to a covalent bond with the Ga atom and needs a H0.75 pseudohydrogen. Through the conditions that reported previously, we performed the optimize run of the AIMPRO on slab mode for each 2x2 cleaved surfaces {(111)B or (100)B, (101), (011), (113)B or (123)B, (124)B, (214)B} of GaAs (112)B structure. The value of vacuum we used was 12 Å in the vertical direction o [...]
doi:10.26262/ fatcat:6hhr43usivhpxnxim5z3zogoeq