Theoretical study of GaAs surface passivation with Se

The mechanism for the quenching of surface states of GaAs by adsorbed elemental Se is studied using atomic clusters in ab initio Hartree–Fock calculations. Both the Ga- and the As-terminated surfaces are tied off with Se atoms in a 2×1 reconstruction. The most stable structure is established as two Se atoms bridging two As atoms. It is found that after termination of Ga and As dangling orbitals with H atoms and passivating the surface with Se, the density of surface states in the bandgap region is appreciably reduced.