Surfaces of GaP and InP: structural motifs, electronic statesand optical signatures

We present ab initio calculations on the energetics and geometry, as well as electronic and optical properties of InP and GaP 001.surfaces. Cation-rich conditions lead to the formation of asymmetric cation–anion dimers on top of a 2=4. reconstructed cation-terminated surface. Anion-rich surfaces form c 4=4.reconstructions. Based on the DFT-LDA electronic structure, we compute the reflectance anisotropy of the energetically favoured 2=4.reconstructions. Strong anisotropies in the low-energy region arise from transitions between s-like cation–cation bonding states and empty dangling bonds. Transitions involving P dimer states and surface modified bulk wave functions contribute at higher energies. The application of GW corrections leads to non-uniform shifts of characteristic peaks and changes the line shape, considerably improving the agreement with experiment. q2000 Elsevier Science B.V. All rights reserved