Phase-transition-induced residual strain in ferromagnetic MnAs films epitaxially grown on GaAs(001)

Abstract

We investigate the atomic interface structure and the residual strain state of ferromagnetic α (hexagonal) MnAs layers on cubic GaAs(001) by means of high-resolution transmission electron microscopy and electron diffraction. Despite the different symmetries of the adjacent planes at the heterointerface and the large and orientation-dependent lattice mismatch, the hexagonal MnAs grows epitaxially on GaAs(001) with the (11̄.0) prism plane parallel to the cubic substrate. The atomic arrangement at the interface, which is defined by the accommodation of the large lattice mismatch, explains this extreme case of heteroepitaxial alignment. The anisotropic residual strain distribution is discussed with respect to the particular process of lattice misfit relaxation in the presence of the ferromagnetic phase transition.

Temperature dependence of the growth morphology in molecular beam epitaxy grown MnAs

“…MnAs films grown on GaAs(0 0 1) in MBE revealed two dominant crystallographic relationship with the substrate [12][13][14][15] : one is the so-called ''type A'', where MnAsð11 0 0Þ plane is parallel to GaAs(0 0 1) plane, and the other is ''type B'', where the MnAsð11 0 1Þ plane is parallel to GaAs(0 0 1). This type conversion in the crystallographic relationship of MnAs with respect to GaAs substrate was controlled by the growth conditions such as T s and beam-equivalent-pressure (BEP) ratio of As 4 /Mn [9].…”

Magnetization reversal and anomalous dependence of the coercive field with temperature in MnAs epilayers grown on GaAs

“…At T St =398 K, a second structural transition takes place and the system regains a NiAs hexagonal structure. MnAs grows epitaxially on various standard semiconductor substrates such as GaAs(100), 4,5,6 GaAs(111)B, 7,8,9 GaAs(110), 10 InP(100), 11 Si(100) 12 and Si(111). 13 The excellent quality of MnAs/GaAs heterostructures makes this compound particularly interesting for hybrid metal/semiconductor spintronics.…”

Epitaxial hybrid ferromagnet-semiconductor structures: growth, structural and magnetic properties

“…Further growth on such a surface proceeds layer-by-layer as evidenced by RHEED intensity oscillations [19]. High-resolution transmission electron microscopy studies show that the MnAs/GaAs interface is smooth and chemically sharp [16].…”

“…1). Two fundamental issues for understanding this unexpected result of real heteroepitaxy have been identified: (i) an interesting anisotropic lattice mismatch accommodation mechanism [16] and (ii) the strain-mediated coexistence of α-and β-MnAs below the bulk phase transformation temperature [17]. By controlling the stoichiometry of the GaAs template and the MnAs growth conditions, several epitaxial orientations can be realized [14,15].…”