Abstract

The recently developed high energy variant of x-ray photoelectron spectroscopy(XPS), known as hard x-ray photoelectron spectroscopy (HAXPES), has been used to study various semiconductor material systems. Extending the photoemission sampling depth to >10 nm into the material surface by the use of monochromatic x-ray photons in the 2 to 4 keV energy range, enables the acquisition of chemical and electronic information deeper into the bulk than is possible with conventional XPS, and facilitates the investigation of multilayer structures. In this study, combined HAXPES and electrical characterisation studies were performed on Si,GaAs and InGaAs based metal-oxide-semiconductor (MOS) structures in order to cross-correlate the electronic information derived from these different measurement methods. The results obtained indicate that surface potential changes at the semiconductor/dielectric interface due to the presence of different work function metals can be detected using HAXPES measurements. Changes in the semiconductor band bending at zero gate voltage and the at band voltage values derived from capacitance-voltage (C-V) measurements are in agreement with the semiconductor core level shifts measured from the HAXPES spectra. Experiments have been performed which utilise the increased sampling depth of HAXPES to chemically and structurally characterise Ni-InGaAs and Mo-InGaAs interface formation. These material systems are of interest as possible source drain contacts for use in future high mobility InGaAs based MOS field-effect-transistors due to their extremely low contact resistance and self-aligned formation. Complementary x-ray absorption spectroscopy (XAS) measurements were used in combination with HAXPES data to develop a model of the chemical interactions and compound formation at the Ni-InGaAs and Mo-InGaAs interfaces as a function of anneal temperature.