Article

Achieving High Curie Temperature in (Ga,Mn)As

Applied Physics Letters (Impact Factor: 3.52). 08/2008; 93(13). DOI: 10.1063/1.2992200
Source: arXiv

ABSTRACT We study the effects of growth temperature, Ga:As ratio and post-growth annealing procedure on the Curie temperature, Tc, of (Ga,Mn)As layers grown by molecular beam epitaxy. We achieve the highest Tc values for growth temperatures very close to the 2D-3D phase boundary. The increase in Tc, due to the removal of interstitial Mn by post growth annealing, is counteracted by a second process which reduces Tc and which is more effective at higher annealing temperatures. Our results show that it is necessary to optimize the growth parameters and post growth annealing procedure to obtain the highest Tc.

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    • "The main advantage of diluted magnetic semiconductors is the fact that their magnetic properties can be successfully controlled by electric field [1] [2]. Despite great advances in epitaxial growth and post-growth low-temperature annealing of (Ga,Mn)As layers their highest Curie temperature T C = 185 K, as measured by superconducting quantum interference device (SQUID) magnetometry [3], is so far much below room temperature, desirable for practical applications. "
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    ABSTRACT: The dilute (Ga,Mn)As became a model ferromagnetic semiconductor, however there is still a disagreement on the source of its magnetism. In this paper, we verify the ellipsometric results and compare them with more precise photoreflectance method, which gives an important insight into the interaction of the Mn-related states with the ones of GaAs valence band. No spectral shifts observed for the E1 and E1þD1 interband transitions in highly doped and annealed (Ga,Mn)As epitaxial layers indicate that the coupling between a detached Mn impurity band and the valence band does not occur. Our findings are supported by the characterizations of the (Ga,Mn)As epitaxial layers with the high resolution transmission electron microscopy and magnetization measurements.
    Applied Physics Letters 07/2014; 105:032408. DOI:10.1063/1.4891329 · 3.52 Impact Factor
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    • "The main advantage of diluted magnetic semiconductors is the fact that their magnetic properties can be successfully controlled by electric field [1] [2]. Despite great advances in epitaxial growth and post-growth low-temperature annealing of (Ga,Mn)As layers their highest Curie temperature T C = 185 K, as measured by superconducting quantum interference device (SQUID) magnetometry [3], is so far much below room temperature, desirable for practical applications. "
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    ABSTRACT: The diluted (Ga,Mn)As became a model ferromagnetic semiconductor, however there is still a disagreement on the source of its magnetism. The divergences arise from the results indicating that the holes mediated ferromagnetism reside in the valence band or the impurity band. Full understanding of character of the Mn states in GaAs can bring the increase of (Ga,Mn)As Curie temperature. In this paper we verify the ellipsometric results and compare with more precise photoreflectance method which gives a new insight into the interactions of Mn impurity states with GaAs valence band. Indeed, E1 and E1+Δ1 inter-band transition energies for highly doped and annealed (Ga,Mn)As epitaxial layers have not confirmed the interaction between detached Mn impurity band and the valence band. Thus, the description with merged Mn states and GaAs valence band is in agreement with our results. Our findings are supported by the high resolution transmission microscopy and magnetization measurements.
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    ABSTRACT: Systematic investigations of the structural and magnetic properties of single crystal GaxMn1−xN films grown by metal organic vapor phase epitaxy are presented. High resolution transmission electron microscopy, synchrotron x-ray diffraction, and extended x-ray absorption fine structure studies do not reveal any crystallographic phase separation and indicate that Mn occupies Ga-substitutional sites in the Mn concentration range up to 1%. The magnetic properties as a function of temperature, magnetic field and its orientation with respect to the c-axis of the wurtzite structure can be quantitatively described by the paramagnetic theory of an ensemble of non-interacting Mn 3+ ions in the relevant crystal field, a conclusion consistent with the x-ray absorption near edge structure analysis. A negligible contribution of Mn in the 2+ charge state points to a low concentration of residual donors in the studied films. Studies on modulation doped p-type GaxMn1−xN/(Ga,Al)N:Mg heterostructures do not reproduce the high temperature robust ferromagnetism reported recently for this system.
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