SURFACE-CHEMISTRY OF INALAS AFTER (NH4)(2)S(X)

The (NH4)2S(x) sulphidation of MBE-grown InAlAs layers was studied in order to passivate GaInAs/InAlAs/InP HEMT microelectronic devices. The chemical composition of sulphurized InAlAs (100) surfaces was investi gated by x-ray photoelectron spectroscopy (XPS). The S-treated surface s were compared with an oxidized chemically etched InAlAs surface (aft er removing the top GaInAs capping layer) and with an 'as-grown' InAlA s surface. It was observed that the InAlAs layers could be completely deoxidized and that, depending on the experimental conditions, a thin (2 monolayers (ML)) or a thick (8 ML) sulphide layer could be prepared . XPS analysis of the sulphide-tested surfaces indicated that oxidatio n was strongly suppressed but that the segregation of elemental As was not effectively suppressed. In the case of thick sulphide layers, str ong chemical passivation occurs, since no degradation of the surface c hemistry was observed after one month's exposure to air.