A study of structure and mixing at the interface between Fe and AlGaAs (100)

The solid-state reaction between monocrystalline AlGaAs(100) and polycrysta lline Fe films, having thickness in the 50-100 nm range, has been investiga ted using X-ray diffraction, conversion electron Mossbauer spectroscopy and transmission electron microscopy. The Fe films were deposited on ion-etche d semiconductor substrates using an ion-beam-sputtering technique. It has b een found that, in the as-deposited state, the thickness of the interfacial zone never exceeds 1.5 nm, a value comparable to that obtained for Fe film s deposited by molecular-beam-epitaxy. The interface reaction of the Fe fil ms was also studied after annealing in vacuum at 400 degreesC for 1 h. The orientation of the magnetization and the grain size of the deposited metall ic layers are reported for the as-deposited, as well as for the annealed fi lms. Interdiffusion after annealing mainly results in the generation of Fe2 As grains. These grains were observed in the AlGaAs substrate, exactly unde r the Fe/AlGaAs interface, and they have a triangular shape; this is the fi rst report on the formation of grains with such a shape. Additional analysi s on the orientation relationship between the Fe2As grains and the substate was carried out and the results are also presented here. Studies concernin g the diffusion of Al, Ga and As atoms into the Fe overlayer revealed the l ow mobility of As, as compared to Al and Ga. (C) 2000 Elsevier Science B.V. All rights reserved.