SOLID-STATE INTERDIFFUSIONS IN EPITAXIAL FE GAAS(001) HETEROSTRUCTURES DURING ULTRAHIGH-VACUUM ANNEALINGS UP TO 450-DEGREES-C/

We have used a set of complementary experimental techniques to charact erize an epitaxial structure (25 nm Fe)/GaAs(001) annealed at 450 degr ees C under ultrahigh vacuum conditions. The solid state interdiffusio n leads to the formation of an epitaxial reaction layer made of Fe2As patches embedded in a Ga rich Fe3Ga2-XAsX ternary phase. The epitaxial character of this layer explains how the usually reported epitaxial g rowth of Fe on GaAs performed in the temperature range of 175 to 225 d egrees C is possible in spite of the species intermixing occurring at the interface. Moreover, the observed grains of Fe2As explain the decr ease of magnetization at the interface in such contact, since Fe2As is an antiferromagnetic alloy. (C) 1998 American Institute of Physics.