A TRANSMISSION ELECTRON-MICROSCOPY STUDY OF INTERFACIAL REACTIONS IN THE FE GAAS SYSTEM/

The reaction between thin Fe films and gallium arsenide is studied usi ng chiefly cross-sectional transmission electron microscopy. Fe films, 50-120 nm in thickness, were deposited onto (100) GaAs substrates by ion-beam sputtering and the Fe/GaAs couples were then annealed under v acuum at temperatures ranging between 400 and 550 degrees C. The prese nce of a thin amorphous intermixed layer at the Fe/GaAs interface is p ointed out in the as-deposited conditions; this layer consists of thre e elements Fe, Ga and As. The determination of the residual internal s tress in the as-deposited Fe films is also performed using the sin(2) psi method and the result is of the order of -2 GPa. Iron starts to re act with GaAs at approximate to 400 degrees C, producing a layered Fe/ Fe3Ga/Fe2As + FeAs/GaAs structure. The sequence suggests that Fe diffu ses into the GaAs and liberates Ga while forming iron arsenides. After annealing, the Fe/GaAs bimaterial also exhibits interfacial undulatio ns which are discussed in terms of strain-energy relaxation.