Alloying behavior at the AuGeNi/GaSb interface: Photoemission studies of the effects of annealing temperature

Abstract

An ultra-thin AuGeNi alloy (84%/12%/4% by weight) overlayer of 5 nm was evaporated onto Te-doped n-type (100) oriented GaSb substrates. Samples were annealed in ultra-high vacuum (UHV), with a base pressure of 10⁻¹⁰ Torr at either 300°C, 500°C, or 700°C for 12 h. The reacted interface was then revealed by Ar ion sputter-depth profiling. The highest percentage of Ge in the deep interface region was observed for the sample annealed at 500°C. Annealing at 500°C also leads to a uniform distribution of Ga, Sb, and Au concentrations. Results show that virtually all Au, Ge, and Ni evaporate away after annealing at 700°C. Au-based AuGa alloy formation was indicated by the shifts of Au 4f core-levels and the metallic Ga 3d peak. The small variation of Au 4f core-levels with sputtering for samples annealed at 500°C is the evidence of AuGa uniform alloying from the surface to the interface. It has been, therefore, concluded that annealing at 500°C forms a more uniform distribution of cluster size throughout the interface than annealing at 300°C or 700°C.