The growth of AuGa2 thin films on GaAs(001) to form chemically unreactive interfaces

Abstract

Thin AuGa₂ films were grown by codeposition from separate Au and Ga evaporation sources on clean GaAs(001) substrates in ultrahigh vacuum, and were studied by Auger electron spectroscopy, electron energy-loss spectroscopy, low-energy electron diffraction, scanning electron microscopy, and x-ray diffractometry. The morphology and crystallinity of the AuGa₂ were highly dependent upon the film deposition and annealing history. Films grown on room-temperature substrates were continuous, specular, and polycrystalline, but the dominant orientation was with the (001) planes of the crystallites parallel to the substrate surface. Annealing to temperatures between 300°and 480°C caused the film to break up and coalesce into rectangular crystallites, which were all oriented with (001) parallel to the surface. An anneal to 500°C, which is above the AuGa₂ melting point, resulted in the formation of irregular polycrystalline islands of AuGa₂ on the GaAs(001) substrate. No interface roughening or chemical reactions between the film and substrate or interface were observed for even the highest-temperature anneals.