The chemical and electronic properties of selenium passivated GaAs(001)-(2 x 1) surfaces were investigated by a combination of theoretical calculations and core level photoemission experiments. An anion exchange results in GaSe-like layers showing a 2 x 1 reconstruction in low energy electron diffraction. The analysis of the different components in the core level spectra of As 3d, Ga 3d and Se 3d limits the number of possible structural models. The Se/GaAs(001)-(2 x 1) reconstruction was also analysed by means of DFT-LDA calculations and theoretical scanning tunnelling microscopy currents. In a first step, different geometries were considered and the most stable one, from the point of view of the thermodynamic potential, was determined. Then, scanning tunnelling microscopy currents and the corresponding surface corrugation were calculated and compared with the experimental evidence. It was concluded that the Se/GaAs(001)-(2 x 1) reconstruction had a single Se atom in the last crystal layer, bonded to two Ga atoms of the second layer, and another Se layer replacing the third As layer of the crystal. These surfaces could be considered as chemically stable because they withstand considerable exposure to air. In terms of electronic passivation, i.e. the removal of any surface band bending, the selenium modification was not successful. Band bending on n-type doped samples was reduced while band bending on the p-type doped samples was further increased.

Selenium Passivation of GaAs(001) - a Combined Experimental and Theoretical Study. C.González, I.Benito, J.Ortega, L.Jurczyszyn, J.M.Blanco, R.Pérez, F.Flores, T.U.Kampen, D.R.T.Zahn, W.Braun: Journal of Physics - Condensed Matter, 2004, 16[13], 2187-206