IMPORTANCE OF DEFECTS AND DOPANT NATURE IN ALKALI-METAL III-V-SEMICONDUCTOR INTERFACE FORMATION AND PROMOTED OXIDATION

The room-temperature oxidation of p- and n-type GaSb(110) surfaces mod ified by a sodium or a rubidium overlayer is investigated by means of core-level and valence-band photoemission spectroscopy using synchrotr on radiation. The oxidation rate of the GaSb(110) is increased by near ly 6 orders of magnitude in the presence of the alkali-metal adsorbate . This results in the formation of mixed Ga2O3 and Sb2O5 oxides. A com plete oxidation of the GaSb(110) surface only occurs when a strong rea ction between the alkali overlayer and the substrate takes place, whic h indicates that defects play a central role in the reaction similarly to the previously observed case of alkali-metal-promoted nitridation of other III-V semiconductor surfaces. This behavior is very different from the one observed in the case of alkali-metal-promoted oxidation or nitridation of elemental semiconductors such as silicon where no re action between the adsorbate and the substrate occurs. Interestingly, the p-type (Zn doped) surfaces were, in general, found to be more reac tive than the n-type (Te doped) ones, which suggests that the nature o f the dopant might also play some role in the formation of reactive in terfaces. The results indicate that surface defects seem to play an im portant role in alkali-metal-promoted reactions of III-V compound semi conductors.