Role of defects in the passivation of III–V semiconductor surfaces modified by alkali metals: O2/Rb/p- and n-type GaSb(110)

Abstract

The effect of rubidium overlayers is investigated on the room-temperature oxidation of GaSb(110) surfaces by means of core-level and valence-band photoemission spectroscopy using synchrotron radiation. The presence of Rb enhances the oxidation rate of the GaSb(110) by at least six orders of magnitude and results in the formation of mixed Ga2O3 and Sb2O5 oxides. A strong reaction between the Rb overlayer and the GaSb surface is found to be essential for a complete oxidation, thus stressing the role of surface defects similarly to the previously observed case of alkali metal-promoted nitridation of GaAs(110) and InP(110) surfaces. This is in strong contrast to the behavior observed for alkali metal promoted oxidation or nitridation of an elemental semiconductor like silicon where no reaction occurs between the catalyst and the substrate. These results suggest that the presence of surface defects appear to play, in general, an important role in alkali-metal-promoted reactions of III–V compound semiconductors. Surprisingly, the interfaces formed with the p-type (Zn-doped) GaSb(110) samples are significantly more reactive than the n-type (Te-doped) one which suggests that the nature of the dopant might be of relevance in the formation of reactive interfaces.