• Korean Journal of Materials Research
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• v.18 no.8
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• pp.444-449
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• 2008

Samples of GaMnAs, GaMnAs codoped with Be, and GaMnAs simultaneously codoped with Be and Mg were grown via low-temperature molecular beam epitaxy (LT-MBE). Be codoping is shown to take the Ga sites into the lattice efficiently and to increase the conductivity of GaMnAs. Additionally, it shifts the semiconducting behavior of GaMnAs to metallic while the Mn concentration in the GaMnAs solid solution is reduced. However, with simultaneous codoping of GaMnAs with Be and Mg, the Mn concentration increases dramatically several times over that in a GaMnAs sample alone. Mg and Be are shown to eject Mn from the Ga sites to form MnAs and MnGa precipitates.

• Journal of Magnetics
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• v.10 no.3
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• pp.103-107
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• 2005

Magnetotransport is a prerequisite to realization of electronic operation of spintronic devices and it would be more useful if realized at room temperature. The effects of Be codoping on GaMnAs on magnetotransport were investigated. Mn flux was varied for growth of precipitated GaMnAs layers under a Be flux for degenerate doping via low-temperature molecular beam epitaxy. Magnetotransport as well as ferromagnetism at room temperature were realized in the precipitated GaAs:(Mn,Be) layers. Codoping of Be was shown to promote formation of MnGa clusters, and annealing process further stabilized the cluster phases. The room-temperature magnetic properties of the layers originate from the ferromagnetic clusters of MnGa and MnAs embedded in GaAs. The degenerately doped metallic GaAs matrix allowed the visualization of the magnetotransport through anomalous Hall effect.

• Journal of the Korean Magnetics Society
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• v.14 no.6
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• pp.213-218
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• 2004

Be-codoped GaMnAs layers were systematically grown via molecular beam epitaxy with varying Mn- and Be-flux. Mn flux was controlled to cover from solid solution type GaMnAs to precipitated GaMnAs. Two Be flux were chosen to exhibit semiconducting and metallic resistivity in the grown layers. The structural, electrical, and magnetic properties of GaAs:(Mn, Be) were investigated. The lightly Be-codoped GaMnAs layers showed ferromagnetism at room temperature, but did not reveal magnetotransport due to small magneto-resistance and high resistance of the matrix. However, room temperature magnetotransport could be observed in the degenerate Be-codoped GaMnAs layers, and which was assisted by the high conductivity of the matrix. The Be-codoping has promoted segregation of new ferromagnetic phase of MnGa as well as MnAs.

• Proceedings of the Korean Magnestics Society Conference
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• 2004.06a
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• pp.26-27
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• 2004

• Korean Journal of Materials Research
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• v.15 no.1
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• pp.73-77
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• 2005

Motivated by the enhanced magnetic properties of Mg-codoped GaMnN ferromagnetic semiconductors, Be-codoped GaMnAs films were grown via molecular beam epitaxy with varying Mn flux at a fixed Be flux. The structural, electrical, and magnetic properties were investigated. GaAs:(Mn,Be) films showed metallic behavior while GaAs:Mn films showed semiconducting behavior as determined by the temperature dependent resistivity measurements. The Hall-effect measurements with varying magnetic field showed clear anomalous Hall effect up to room temperature proving ferromagnetism and magnetotransport in the GaAs:(Mn,Be) films. Planar Hall resistance measurement also confirmed the properties. The dramatic enhancement of the Curie temperature in GaMnAs system was attributed to Be codoping in the GaMnAs films as well as MnAs precipitation.