Solid state interdiffusions in epitaxial Fe/GaAs(001) heterostructures during ultrahigh vacuum annealings up to 450 °C

Abstract

We have used a set of complementary experimental techniques to characterize an epitaxial structure (25 nm Fe)/GaAs(001) annealed at 450 °C under ultrahigh vacuum conditions. The solid state interdiffusion 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 growth of Fe on GaAs performed in the temperature range of 175 to 225 °C is possible in spite of the species intermixing occurring at the interface. Moreover, the observed grains of Fe2As explain the decrease of magnetization at the interface in such contact, since Fe2As is an antiferromagnetic alloy.

A study of interdiffusion phenomena at the interface between Fe and Al0.25Ga0.75As(001)

“…In particular, this type of environment can be found in the Fe 3 Ga alloy [28]. Here we suggest to consider the Fe 3 Ga 2−x As x compounds with 0.15 ≤ x ≤ 1.1 for the following reasons: (i) the Fe 3 Ga 2−x As x phase is in thermodynamic equilibrium with GaAs at ∼600 • C in the Fe-Ga-As ternary phase-diagram [20], (ii) phases with x ∼ 0.2 have been already detected in Fe/GaAs [13] after annealing at 450 • C, and (iii) the XRD experiments reported in Section 3.1 showed two weak reflections which could be attributed to Fe 3 Ga 2−x As x . From the Mössbauer studies in [21,22], it appears that the hmf average values for the Fe 3 Ga 2−x As x compounds, measured at room temperature, strongly increase with decreasing x value.…”

“…The structural changes, taking place at the heterointerface after 1 h annealing at temperatures ranging between 400 and 500 • C, were chiefly investigated using X-ray diffraction (XRD) and conversion electron Mössbauer spectroscopy (CEMS). The obtained results will be compared to those of recent studies of Fe/GaAs couples prepared by MBE deposition [13,14].…”

Effect of thermal annealing of high temperature growth [(GaAs) m (Fe) n ] p composite films on GaAs(001) by molecular beam epitaxy

“…The absorption and magneto-optical properties of GaAs : MnAs are strongly dependent on its cluster size. On the other hand, by annealing Fe/GaAs(001) films at above 500 o C, precipitation of Fe 3 GaAs is found with Fe 3 Ga and Fe 2 As compounds [9][10][11][12].…”

Ab initioinvestigation of FeAs/GaAs heterostructures for potential spintronic and superconducting applications

“…However spin injection in Fe/GaAs has not yet proven successful 9 . One possible reason for this is the formation of other phases at the interface; indeed FeAs and Fe 2 As have both been reported experimentally [10][11][12][13] , and ab initio calculations suggest that Fe penetrates the GaAs lattice, breaking the Ga-As bonds in favor of Fe-As and elemental Ga 14 .…”