Successful growth of (100)ErAs single-crystal films on (100)GaAs has been demonstrated. Reflection high-energy electron diffraction, low-energy electron diffraction (LEED), and Rutherford backscattering with channeling indicate single-crystal growth. LEED from the ErAs shows a (1×1) structure. Overgrowth of GaAs on ErAs is found to be difficult due to the GaAs not wetting the ErAs surface and hence resulting in island growth. For a 150-Å-thick film metallic behavior is observed with resistivities 17 and 70 μΩ cm at 1.5 K and room temperature, respectively. Low-temperature Hall measurements show the conduction to be dominated by electrons with an effective n-type mobility in the range 360 cm2/V s at 1.35 K.

The reaction kinetics of Al with Ti22W78 alloys has been investigated under vacuum annealing conditions. In particular, the effects of Cu in Al and venting during deposition of TiW were studied. It was observed that Cu did not play any significant role in the kinetics of the interdiffusion of Al and TiW. During the reaction process at temperatures around 500 °C, Ti accumulated on the surface of the samples with or without Cu in Al. The Ti accumulation is diffusion limited with an activation energy of 2.4 eV. Interface oxides are believed to be primarily responsible for the stability of Al/TiW metallization.

In situ scanning tunneling microscopy and x-ray photoelectron spectroscopy were combined to examine the formation of the Fe/GaAs interface for Fe films grown on GaAs(100) As-rich surfaces by molecular beam epitaxy. Scanning tunneling microscopy images acquired following the growth of ultrathin layers of Fe on GaAs (2×4)/c(2×8)β2 surfaces show the initial growth of Fe results in little disruption of the As-dimer rows located directly adjacent to the deposited Fe clusters for growth temperatures between −15 and 175 °C. X-ray photoemission spectra show the interfacial Fe–Ga–As reactions depend on the growth temperature and can be minimized by growing at temperatures below 95 °C. However, approximately 0.7 ML of As was found to segregate to the Fe surface during growth, independent of the growth temperature. Atomic layer-by-layer calculations of the normalized intensity curves obtained from x-ray photoemission were used to quantify the extent of the interfacial reactions as a function of growth temperature. A 5 ML thick (∼14 Å) ErAs interlayer was used as a diffusion barrier to further limit the Fe–Ga–As interfacial reactions. For Fe growth at 225 °C on ErAs interlayers, the extent of the interfacial reactions was found to be comparable with the extent of the reactions resulting from the growth of Fe directly on GaAs at −15 °C. Although the ErAs interlayers suppressed the reactions between Fe and GaAs at the interface, they were unable to significantly alter the amount of As segregating to the Fe surface during growth.

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The use of thermodynamically stable epitaxial metal/GaAs contacts fabricated by molecular-beam epitaxy has enabled detailed studies of Schottky barrier formation on well characterized and controlled structures. The effects of lattice mismatch, annealing and substrate orientation on the barrier height of Sc1−xErxAs semimetal contacts on n-GaAs are studied. The barrier height could be varied from ∼1.03 eV for Sc1−xErxAs films grown at 350–400 °C and annealed at ∼600 °C on (100) GaAs to ∼0.63 eV for films grown at ∼600 °C on (1̄1̄1̄) GaAs.