Combined analysis of overlayer/S/GaAs interfaces with photoemission spectroscopy and X-ray standing wave

• Published in: Applied surface science 1993-01, Vol.70 (1-4), p.496-501
• Main Authors: Oshima, M., Scimeca, T., Sugiyama, M., Maeyama, S., Oigawa, H., Nannichi, Y., Hashizume, H.
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Diffusion; interface formation; Electron and ion emission by liquids and solids; impact phenomena; Exact sciences and technology; Interfaces, heterostructures, nanostructures; Photoemission and photoelectron spectra; Physics; Solid surfaces and solid-solid interfaces; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties)
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/0169-4332(93)90568-V

Metal/GaAs or insulator/GaAs interfaces with a sulfur interlayer have been investigated using photoemission spectroscopy and the X-ray standing wave (XSW) method in order to determine the structure and chemical bonding at the interface and further correlate this with the electrical properties. It is found that while a CaF 2 overlayer is not very reactive towards the S interlayer, deposited Al strongly reacts with the surface S-Ga layer to form a thermodynamically stable Al-S interface monolayer, which plays a role in achieving metal-dependent Schottky contact. On the other hand, reactive Pd metal disrupts the S-passivated GaAs surfaces, resulting in surface segregation of sulfur. In this case, the Schottky barrier heights are identical to Pd/GaAs, indicating the importance of S remaining at the interface. XSW analysis reveals that the CaF 2 and Al/S/GaAs systems have well-ordered interfaces. Thus, the stability of the S passivation layer is discussed in terms of the S-Ga binding energy and the reactivity of the deposited overlayer.