Comparison of chemically inert and reactive metal-compound-semiconductor interfaces: AuGa 2 and gold on GaSb(001)

Abstract

AuGa 2-GaSb(001) and Au-GaSb(001) interfaces were prepared by molecular beam deposition and studied using Auger electron spectroscopy (AES), low energy electron diffraction (LEED), electron energy loss spectroscopy, scanning electron microscopy and X-ray microprobe analysis. AuGa 2 was chosen as an inert contact because it terminates a pseudobinary tie-line in the Au-Ga-Sb ternary phase diagram. Annealing a AuGa 2 film 500 Å thick (deposited with a small excess of gallium) on GaSb to 747 K yielded islands of AuGa 2 and gallium, residing on top of a relatively smooth and flat substrate. In contrast, a gold film 500 Å thick annealed to 723 K reacted chemically with the substrate resulting in the formation of islands consisting of Au-Ga compound phase(s) and gross pitting of the GaSb(001) surface. An LEED-AES study of the annealing behavior of a gold film 40 Å thick on GaSb(001) showed that gold reacts with GaSb even at room temperature. The resultant Au-Ga phase(s) in the film coalesce into islands above about 500 K. The chemical inertness of the AuGa 2 and the reactivity of the gold thin films are entirely consistent with the bulk thermodynamic properties of the Au-Ga-Sb system.