Chemical composition of anodic oxides grown on lightly doped ptype InP have been investigated by XPS. Anodization was performed in the constant current density (J,) mode using an ortho-phosphoric acid solution mixed with acetonitrile (ACN). The electrolyte was chosen after experimentation on the effect of the anudiition parameters (electrolyte, viscosity of the electrolyte and pH, J, and illumination level) and annealing conditions on the uniformity and stability of the oxide and the contamination level, as determined by SEMPDAX, SIMS and XPS. Based on our XPS investigation, it appears that the inhomogeneity with depth of the anudii oxides grown on ptype InP is strongly dependent on the growth conditions. Depending on the anodization procedure, the anodic oxide In recent years, indium phosphide has proved to be a very promising semiconductor material for various applications owing to its intrinsic properties, such as high electron mobility and high radiation tolerance. Hence, major attention is beginning to be devoted to InP owing to its potential applications, such as highspeed electronic and integrated opto-electronic devices and high-performance radiation-resistant space solar cells. All these applications are not yet technologically mature and more studies are needed before highperformance devices can be realized.One of the major problems yet to be solved in InP technology is to form insulators on the InP surface that have good chemical stability and dielectric and interface properties. Such insulators are needed in applications requiring surface passivation and for selective etching during device fabrication. Surface passivation is obtained by growth of an insulating layer (extrinsic passivation), which compensates the surface states so that the surface recombination velocity (SRV) is greatly reduced.Based on previously reported information on the insulators formed on InP (e.g. as gate insulators for MISFETS),'-3 the ideal insulator for surface passivation and selective etching should have the following bulk and interfacial properties:

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X-ray photoelectron spectroscopy was employed, in conjunction with ion bombardment, to analyze the chemical composition profile across thin (<50 nm) oxide films on chemically vapor deposited Si3N4. The thermal oxides were grown in dry oxygen at ll00~ on samples with or without native oxide film (formed in room air). The results show that the thermal oxidation product was silicon oxynitride of graded N:O ratio, and that the presence of a native oxide film promotes the formation of a SiO2 crust over the oxynitride. It is proposed that the fundamental mechanism of Si3N4 oxidation is progressive O-for-N substitution in the silicon oxynitride unit tetrahedron, which is best designated SiN3 =O2 § where x is also an index of depth. The corresponding equation for nonstoichiometric oxidation of Si3N4 describes a bulk (rather than an interface) reaction process, with significant implications for O2 and N2 fluxes and diffusivities.

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