Modification of the GaInAsP(100) surface by oxidation and sulfur passivation

The quaternary III-V compound semiconductor (GaInAsP) is one of the important materials for optoelectronic devices such as long-wavelength semiconductor lasers. Understanding its surface chemistry, which is subjected to oxidation, and sulphur passivation, a widely used passivation technique, is of importance for its use for device fabrication. In this study, modification of the quaternary GaInAsP(100) surfaces was performed by UV/ozone and wet chemical oxidation, dilute HF etching, and sulfur passivation. The surface chemistry and composition of the oxidized, oxide-free, and the sulfur-passivated surfaces were measured by X-ray photoemission spectroscopy (XPS). It was found that oxidation by wet chemical etching resulted in preferential oxidation while, oxidation by ozone exposure formed multiple oxide phases of all the constituent elements. Both the HF etch and sulfur-passivation treatment were effective in generating surfaces having no oxide. Preliminary data on surface Fermi-level changes induced by the above surface treatments indicated that both the HF etch and sulfur-passivation treatment reduced the surface-state density on an oxidized surface.