Chalcogen passivation of GaAs(111)B surfaces

The passivation of GaAs surface by either S or Se has received considerable attention. It has long been thought that the Se- or S-treated GaAs(111)B-(1×1) surface has a simple structure, the Se- or S-terminated model. Recently, the atomic structure of the Se-treated GaAs(111)B surface has been revisited and another structure model of the Se-treated surface has been proposed, the mixed Se/As-terminated model. It has been reported in our previous study that the Se-terminated and the mixed Se/As-terminated surfaces are stable in the phase diagram at 0K as functions of the chemical potentials of Se and As. In this study, we have investigated the stability of Se-or S-treated GaAs(111)B surface structures by considering the influence of growth conditions, such as a partial pressure of the gas molecule and a growth temperature using the first-principles calculations within the density functional theory. We have found that the mixed Se/As-terminated surface is stable, being consistent with the recent experimental results. Surprisingly, the Se-terminated surface becomes stable as the Se pressure increases, even though this surface does not satisfy the so-called electron-counting rule.