Thin Solid Films 446 (2004) 6–11 0040-6090/04/$ - see front matter  2003 Elsevier B.V. All rights reserved. doi:10.1016/S0040-6090Ž03.01232-X Fe GaAs y GaAs(001): a stable and magnetic metal-semiconductor 3 heterostructure B. Lepine *, C. Lallaizon , P. Schieffer , A. Guivarc’h , G. Jezequel , A. Rocher , F. Abel , a, a a a a b c ´ ´´ C. Cohen , S. Deputier , F. Nguyen Van Dau c d e ´ Equipe de Physique des Surfaces et des Interfaces, UMR CNRS-Universite no. 6627, Bat. 11C, Campus de Beaulieu, F 35042 Rennes Cedex, a ´ ˆ France CEMES CNRS, 29 rue Jeanne Marvin, BP 4347, F 31055 Toulouse Cedex, France b Groupe de Physique du Solide, UMR CNRS-Universite no. 7588, Universites Paris VI et VII, Tour 23-2, place Jussieu, F 75251 Paris Cedex, c ´ ´ France Laboratoire de Chimie du Solide et Inorganique Moleculaire, UMR CNRS-Universite no. 6511, Campus de Beaulieu, F 35042 Rennes Cedex, d ´ ´ France UMR CNRS-Thales no. 137, Domaine de Corbeville, F 91404 Orsay, France e Received 26 June 2003; received in revised form 24 July 2003; accepted 17 August 2003 Abstract WeshowthatinagreementwiththeternaryFe–Ga–Asphasediagram,thesolid-stateinterdiffusionsinepitaxialFeyGaAs(001) heterostructures lead, at a temperature of approximately 500 8C, to the formation of thermodynamically stable Fe GaAsy 3 GaAs(001) contacts quite similar to the well-known silicideySi ones. The Fe GaAs films are made of grains epitaxial on GaAs 3 with a well-defined interface. Their magnetic and electrical properties make Fe GaAs on GaAs an attractive metallization scheme 3 for future magnetoelectronic devices. The results we report concern (25 or 80 nm Fe)yGaAs(001) heterostructures annealed at 480 and 500 8C for 10 min and characterized ex situ by He Rutherford backscattering and ion channeling, X-ray diffraction, q transmission electron microscopy and alternating gradient field magnetometry.  2003 Elsevier B.V. All rights reserved. PACS: 68.55a; 81.15Np; 81.05.Ea; 75.50.Cc Keywords: Solid phase epitaxy; Gallium arsenide; Iron; Magnetic properties 1. Introduction The growth of ferromagnetic films on semiconductor substrates has received much attention over the past decade. The combination of the magnetism of the metallic layer along with the electronic properties of the semiconductor substrate offers the opportunity for inno- vative magnetotransport effects and devices to be real- ized. However, because the two types of materials are very dissimilar in terms of physical, chemical and structural properties, integration of semiconductors and ferromagnets is generally very difficult w1–4x. *Corresponding author. Tel.: q33-2-23-23-69-21; fax: q33-2-23- 23-61-98. E-mail address: bruno.lepine@univ-rennes1.fr (B. Lepine). ´ The (ferromagnetic metal) yGaAs systems have been widely studied in the last few years, in particular the epitaxial Fe yGaAs heterostructures w3,4x. However, due to a strong reactivity between ferromagnetic metals and GaAs,theresultingstructuresarenotthermodynamically stable. The purpose of this study is to obtain epitaxial and stable (magnetic compound) yGaAs structures by inducing a controlled thermal interaction between a metal film and a GaAs substrate. Many studies have been dealing with the metal yGaAs solid-state interdif- fusions during annealing treatments but, as in the cases of CoyGaAs w5x and Ni yGaAs w6,7x contacts, the final step of the interaction was always found to be a mixture of binary or ternary compounds w1,2,5,6x:thermodynam- ically stable and epitaxial contacts equivalent to the CoSi ySi, NiSi ySi and CrSi heterostructures w8x have 2 2 2