Abstract
We have studied the formation and properties of ≊15 nm films of Pd on GaAs(100) and (110) substrates as a function of annealing temperature. Ultraviolet and x–ray photoelectron spectra (UPS and XPS) have established several distinctive phases; coupled with scanning electron microscopy studies, agglomeration has been observed at elevated temperatures. Transmission electron diffraction studies permit more detailed phase identification at specific temperatures. Electrical studies permit characterization of both interface properties and bulk transport properties of the reacted layer. In contrast to previous work, we find no Pd–As binary phases. After high temperature anneals (T
a
>350 °C), only PdGa is observed; these films are not continuous, but form [often epitaxial on (100) substrates—with (110)PdGa‖‖ (100)GaAs and [1̄11]‖‖[011]GaAs] islands. After low temperature (≊250 °C) anneals of Pd films on (110) substrates, small crystallites of PdGa are imbedded in the dominant matrix of a ternary single crystal phase. Energy dispersive x‐ray analysis and XPS core level intensities suggest that this phase has the nominal composition of Pd2GaAs. Metallic Ga is inferred after room temperature deposition from He ii UPS studies of the Ga 3d core level.