| 1. |
- Ivanov, S.V., et al.
(author)
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MBE growth and properties of bulk BeCdSe alloys and digital (BeSe : CdSe)/ZnSe quantum wells
- 2000
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In: Journal of Crystal Growth. - 0022-0248 .- 1873-5002. ; 214, s. 109-114
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Journal article (peer-reviewed)abstract
- We report for the first time on MBE growth, structural and optical properties of single layers, quantum well structures and short-period superlattices based on BexCd1-xSe ternary alloys on GaAs. Both the conventional MBE growth mode and the sub-monolayer digital alloying technique (SDA) have been employed for the fabrication of the structures. Compositional boundaries of an instability region 0.03 < x < 0.38, calculated in a regular solution approximation for the completely coherent system, agree well with available experimental data. A suppression of the phase separation in BeCdSe by elastic stress in the layer, accompanied by a strong reduction of the Cd incorporation coefficient has been found. Ultrathin 2.8 ML BeCdSe SDA QWs with x approx. 0.15 demonstrate about an order of magnitude increase in the PL intensity with respect to the pure CdSe one, probably resulting from an enhanced carrier localization efficiency. Eg as a function of the Be content reveals a strong bowing in optical data, which allows one to consider BeCdSe alloys with compositions nearly lattice-matched to GaAs as potential materials for the active region of blue-green lasers.
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| 2. |
- Buyanova, Irina, 1960-, et al.
(author)
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Control of spin functionality in ZnMnSe-based structures : Spin switching versus spin alignment
- 2003
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 82:11, s. 1700-
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Journal article (peer-reviewed)abstract
- The ability of attaining desired spin functionality by adjusting structural design is demonstrated in diluted magnetic semiconductor (DMS) quantum structures based on II-VI semiconductors. The following spin enabling functions are achieved by tuning the ratio between the rates of exciton spin relaxation within the DMS and exciton escape from it to an adjacent nonmagnetic spin detector. Spin switching is realized when using a thin layer of Zn0.95Mn0.05Se as a spin manipulator and is attributed to a fast exciton escape from the DMS preceding the spin relaxation. Spin alignment is accomplished in tunneling structures where the presence of an energy barrier inserted between a spin manipulator (a DMS-based superlattice) and a spin detector ensures a slow escape rate from the DMS layer.
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| 3. |
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| 4. |
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| 5. |
- Buyanova, Irina, 1960-, et al.
(author)
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Exciton Spin Manipulation in ZnMnSe-Based Structures
- 2003
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Conference paper (peer-reviewed)abstract
- Strong effect of structural design on spin functionality is observed in quantum structures based on II-VI semiconductors. Spin switching is realized when using a thin layer of Zn0.95Mn0.05Se diluted magnetic semiconductor (DMS) as a spin manipulator. This is evident from the polarization of photoluminescence related to a spin detector (an adjacent nonmagnetic quantum well (QW)) measured under the resonant excitation of the spin-up and spin-down states of the DMS, which is identical in value but opposite in sign. The achieved spin switching is suggested to reflect fast carrier diffusion from the DMS due to the absence of an energy barrier between the upper spin state of the DMS layer and the QW. On the other hand, the spin alignment is accomplished in the tunneling structures where the presence of the energy barrier inserted between a spin manipulator (i.e., a ZnMnSe/CdSe DMS superlattice) and a spin detector ensures a slow escape rate from the DMS layer.
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| 6. |
- Buyanova, Irina, 1960-, et al.
(author)
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On the spin injection in ZnMnSe/ZnCdSe heterostructures
- 2002
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Conference paper (peer-reviewed)abstract
- We present results from a detailed study of spin injection in thin II-VI wide band gap semiconductor heterostructures by magnetooptical spectroscopy. It is shown that efficient spin alignment can be achieved in a diluted magnetic semiconductor barrier (a layer of ZnMnSe or ZnMnSe/CdSe superlattice) as thin as 10 nm. Rather efficient spin injection from such a thin spin aligner to a non-magnetic quantum well is demonstrated, even when the tunneling energy barrier is as thick as 10 nm. The effect of spin relaxation process on spin injection is also closely examined.
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| 7. |
- Buyanova, Irina, 1960-, et al.
(author)
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Resonant suppression of exciton spin relaxation in Zn0.96Mn0.04Se/CdSe superlattices
- 2003
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In: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 93:10, s. 7352-
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Journal article (peer-reviewed)abstract
- Spin relaxation processes in strained Zn0.96Mn0.04Se/CdSe superlattices are studied in detail by using hot photoluminescence combined with tunable excitation spectroscopy. A drastic enhancement in occupation of the upper-lying |+1/2,-3/2> state of the heavy-hole excitons is observed when excitation photon energy is resonantly tuned near an integer number of the LO phonon energy above the |+1/2,-3/2> state. Assuming the Boltzmann distribution between the excitonic states, the spin temperature of the excitons is deduced to be as high as 85 K, well above the lattice temperature of 2 K. The observed behavior provides experimental evidence for a surprisingly strong suppression of spin relaxation from the upper spin-split excitonic branch for small values of wave vector.
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| 8. |
- Buyanova, Irina, 1960-, et al.
(author)
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Tunable laser spectroscopy of spin injection in ZnMnSe/ZnCdSe quantum structures
- 2002
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 81:12, s. 2196-
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Journal article (peer-reviewed)abstract
- Magneto-optical spectroscopy in combination with tunable laser excitation is employed to study exciton spin alignment and injection in ZnMnSe/ZnCdSe quantum structures. This approach enables us to selectively create preferred spin orientation and to separately monitor subsequent spin injection from individual spin states, thus shedding light on a possible source of spin loss. It is shown that the limited spin polarization in a nonmagnetic quantum well due to spin injection from a ZnMnSe-based diluted magnetic semiconductor (DMS) is not caused by a limited degree of spin alignment in the DMS, which is in fact complete, but rather occurs during subsequent processes.
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| 9. |
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| 10. |
- Chen, Weimin, 1959-, et al.
(author)
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Efficient spin depolarization in ZnCdSe spin detector : an important factor limiting optical spin injection efficiency in ZnMnSe/CdZnSe spin light-emitting structures
- 2004
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 85, s. 5260-
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Journal article (peer-reviewed)abstract
- Spin depolarization of a ZnCdSe quantum-well spin detector (SD) in ZnMnSe/ZnCdSe light-emitting quantum structures is investigated by cw and time-resolved optical orientation spectroscopy. It is shown that spin depolarization is governed by three distinct spin relaxation processes with the corresponding polarization decay times of 850, 30, and <10 ps. The dominant and the fastest process is attributed to spin relaxation accompanying energy relaxation of hot excitons (and hot carriers) within the SD, providing evidence that it can be an important source of spin loss, leading to the observed limited efficiency of optical spin injection in the structures.
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