Kinetics of MnAs growth on GaAs(001) and interface structure

Abstract

On different As-rich GaAs(001) templates, well characterized by reflectance difference spectroscopy, nucleation and growth of NiAs-type MnAs is investigated in real time by reflection high-energy electron diffraction. Using very high As4/Mn flux ratios and low growth rates, one of the two occurring azimuthal alignments of the (1̄100) orientation can be nearly suppressed even in the nucleation stage, and it vanishes completely with further growth. Annealing is found to be very effective in surface smoothing. In dependence on the As/Mn ratio the MnAs(1̄100) surface develops different reconstructions. This finding is important for further investigations in the growth of double heterostructures. High-resolution transmission electron microscopy of as-grown MnAs/GaAs samples reveals an abrupt interface. The lattice mismatch accommodation is anisotropic with regularly arranged misfit dislocations along the [1̄10] direction and less localized coherency strain in the [110] direction, consistent with a near-coincidence-site lattice model.

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

“…1(b)]; 7 while for the growth on GaAs(100) substrate, two orientations of the epilayer have been described. 4 By correctly adjusting the growth conditions, it becomes possible to obtain one single phase 19 with the MnAs c-axis parallel to the GaAs [110] that lies inside the surface plane [ Fig. 1(b)].…”

Effects of anisotropic exchange on the micromagnetic domain structures

“…We investigate the effects of anisotropic exchange in an artificial material system, starting from the known parameters of MnAs on GaAs(001) [16,17]. MnAs is a hexagonal crystal in its ferromagnetic phase, which exhibits two phase transitions, one of first order at 1 40 T = ∞C from ferromagnetic to nonferromagnetic [18], and one of second order at 2 130 T = °C to a paramagnetic state [19,20].…”

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

“…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]. Our films were grown at conditions (substrate temperature 250…”

“…Ferromagnetic MnAs can be grown epitaxially on GaAs(001), although the lattice mismatch is very large and anisotropic, i.e., 7.5% along the GaAs[110] direction and about 30% along the GaAs[110] direction [14,15] (see Fig. 1).…”