Defect formation on the GaSb (001) surface induced by hydrogen atom adsorption

Density functional theory has been used to characterize the effects of adsorbed H on the electronic structure of the GaSb (001)-α(4×3) surface, which consists of a combination of Ga-Sb and Sb-Sb dimers. Adsorption of two H atoms at a Ga-Sb adatom dimer either has little effect on surface states above the bulk valence band maximum (VBM) or else eliminates them, depending on the mode of adsorption. However, adsorption at the Sb-Sb dimer in the terminating layer produces a state farther into the gap at ~0.10 eV above the clean-surface VBM. Relaxation accompanying the breaking of the Sb-Sb dimer bond leads to increased interactions involving three-fold-coordinated Sb sites in the terminating layer, which in turn raises the energies of the non-bonding lone-pair orbitals. This defect state, which appears to be unique to the reconstructed GaSb (001) surface, could potentially function as a hole trap on the surface of p-type GaSb.