| 1. |
- Gluba, L., et al.
(författare)
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On the nature of the Mn-related states in the band structure of (Ga,Mn)As alloys via probing the E-1 and E-1 + Delta(1) optical transitions
- 2014
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 105:3
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Tidskriftsartikel (refereegranskat)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 E-1 and E-1 + Delta(1) 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. (c) 2014 AIP Publishing LLC.
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| 2. |
- Yastrubchak, O., et al.
(författare)
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Effect of low-temperature annealing on the electronic- and band-structures of (Ga,Mn) As epitaxial layers
- 2014
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Ingår i: Applied Physics Reviews. - : AIP Publishing. - 1931-9401. ; 115:1
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Tidskriftsartikel (refereegranskat)abstract
- The effect of outdiffusion of Mn interstitials from (Ga,Mn) As epitaxial layers, caused by post-growth low-temperature annealing, on their electronic- and band-structure properties has been investigated by modulation photoreflectance (PR) spectroscopy. The annealing-induced changes in structural and magnetic properties of the layers were examined with high-resolution X-ray diffractometry and superconducting quantum interference device magnetometry, respectively. They confirmed an outdiffusion of Mn interstitials from the layers and an enhancement in their hole concentration, which were more efficient for the layer covered with a Sb cap acting as a sink for diffusing Mn interstitials. The PR results demonstrating a decrease in the band-gap-transition energy in the as-grown (Ga,Mn) As layers, with respect to that in the reference GaAs one, are interpreted by assuming a merging of the Mn-related impurity band with the GaAs valence band. Whereas an increase in the band-gap-transition energy caused by the annealing treatment of the (Ga,Mn) As layers is interpreted as a result of annealing-induced enhancement of the free-hole concentration and the Fermi level location within the valence band. The experimental results are consistent with the valence-band origin of itinerant holes mediating ferromagnetic ordering in (Ga,Mn) As, in agreement with the Zener model for ferromagnetic semiconductors. (C) 2014 AIP Publishing LLC.
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| 3. |
- Yastrubchak, O., et al.
(författare)
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Ferromagnetism and the electronic band structure in (Ga,Mn)(Bi,As) epitaxial layers
- 2014
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 105:7
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Tidskriftsartikel (refereegranskat)abstract
- Impact of Bi incorporation into (Ga,Mn)As layers on their electronic-and band-structures as well as their magnetic and structural properties has been studied. Homogenous (Ga,Mn)(Bi,As) layers of high structural perfection have been grown by the low-temperature molecular-beam epitaxy technique. Post-growth annealing treatment of the layers results in an improvement of their structural and magnetic properties and an increase in the hole concentration in the layers. The modulation photoreflectance spectroscopy results are consistent with the valence-band model of hole-mediated ferromagnetism in the layers. This material combines the properties of (Ga,Mn)As and Ga(Bi,As) ternary compounds and offers the possibility of tuning its electrical and magnetic properties by controlling the alloy composition. (C) 2014 AIP Publishing LLC.
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| 4. |
- Yastrubchak, O., et al.
(författare)
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Ion-Implantation Control of Ferromagnetism in (Ga,Mn)As Epitaxial Layers
- 2010
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Ingår i: Journal Of Electronic Materials. - : Springer Science and Business Media LLC. - 0361-5235 .- 1543-186X. ; 39:6, s. 794-798
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Konferensbidrag (refereegranskat)abstract
- Epitaxial layers of (Ga,Mn)As ferromagnetic semiconductor have been subjected to low-energy ion implantation by applying a very low fluence of either chemically active, oxygen ions or inactive ions of neon noble gas. Several complementary characterization techniques have been used with the aim of studying the effect of ion implantation on the layer properties. Investigation of their electrical and magnetic properties revealed that implantation with either O or Ne ions completely suppressed both the conductivity and ferromagnetism in the layers. On the other hand, Raman spectroscopy measurements evidenced that O ion implantation influenced optical properties of the layers noticeably stronger than did Ne ion implantation. Moreover, structural modifications of the layers caused by ion implantation were investigated using high-resolution x-ray diffraction technique. A mechanism responsible for ion-implantation-induced suppression of the conductivity and ferromagnetism in (Ga,Mn)As layers, which could be applied as a method for tailoring nanostructures in the layers, is discussed in terms of defects created in the layers by the two implanted elements.
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| 5. |
- Yastrubchak, O., et al.
(författare)
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Photoreflectance study of the fundamental optical properties of (Ga,Mn) As epitaxial films
- 2011
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 83:24
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Tidskriftsartikel (refereegranskat)abstract
- Fundamental optical properties of thin films of the (Ga,Mn) As diluted ferromagnetic semiconductor with low (1%-2%) and high (4%-6%) Mn content and of a reference GaAs film, grown by low-temperature molecular-beam epitaxy, have been investigated by photoreflectance (PR) spectroscopy. In addition, the films were subjected to complementary characterization by means of superconducting quantum interference device magnetometry, Raman spectroscopy, and high-resolution x-ray diffractometry. Thorough full-line-shape analysis of the PR spectra, which enabled determination of the E-0 electronic transition in (Ga,Mn) As, revealed significant differences between the energy band structures in the vicinity of the Gamma point of the Brillouin zone in the investigated (Ga,Mn) As films. In view of the experimental results obtained, the evolution of the valence band structure in (Ga,Mn) As with increasing Mn content is discussed, pointing to a merging of the Mn-related impurity band with the host GaAs valence band for high Mn content.
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