| 1. |
- Evropeytsev, E. A., et al.
(författare)
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Structural properties and vertical transport in ZnSe/CdSe superlattices grown on an In0.3Ga0.7As metamorphic buffer layer
- 2016
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Ingår i: PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 13 NO 7-9. - : WILEY-V C H VERLAG GMBH. ; , s. 503-506
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Konferensbidrag (refereegranskat)abstract
- We report on the growth by molecular-beam epitaxy of short-period ZnSe/ CdSe superlattices (SLs) on an In0.3Ga0.7As metamorphic buffer layer. Such SLs are considered as a promising material for a wide band-gap photoactive p-n junction in a hybrid monolithic Ge/InxGa1-xAs/In-y(Al,Ga)(1-y)As/II-VI solar cell. Lattice-matching of the SLs to the In0.3Ga0.7As layer is confirmed by X-ray diffractometry. Vertical transport of photoexcited carriers is investigated by means of both steady state and time-resolved photoluminescence techniques in heterostructures containing the ZnSe/CdSe SL with an enlarged quantum well (EQW). Characteristic times of the carrier transport across the SL towards EQW are evaluated in the temperature range 120-300 K. (C) 2016 WILEY-VCH Verlag GmbH amp; Co.
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| 2. |
- Buyanova, Irina A., et al.
(författare)
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Effect of momentum relaxation on exciton spin dynamics in diluted magnetic semiconductor ZnMnSe CdSe superlattices
- 2005
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 71:16
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Tidskriftsartikel (refereegranskat)abstract
- cw hot photoluminescence (PL) complemented by transient PL measurements is employed to evaluate momentum and spin relaxation of heavy hole (HH) excitons in ZnMnSe CdSe superlattices. The rate of acoustic-phonon assisted momentum relaxation is concluded to be comparable to the total rate of exciton decay processes, about (2-3) × 1010 s-1, independent of applied magnetic fields. In magnetic fields when the Zeeman splitting ? of the exciton states is below the energy of the longitudinal optical (LO) phonon (?LO), a surprisingly strong suppression of spin relaxation rate from the bottom of the upper spin band is observed, which becomes comparable to that of momentum scattering via acoustic phonons. On the other hand, dramatic acceleration of the spin relaxation process by more than one order of magnitude is found for the excitons with a high momentum K. The findings are interpreted as being due to electron and hole spin flip processes via exchange interaction with isolated Mn2+ ions. Experimental evidence for the efficient interaction between the hot excitons and Mn impurities is also provided by the observation of spin flip transitions within Mn2+ - Mn2+ pairs that accompany the momentum relaxation of the hot HH excitons. In higher magnetic fields ?= ?LO, abrupt shortening of the spin flip time is observed. It indicates involvement of a new and more efficient spin relaxation process and is attributed to direct LO-assisted exciton spin relaxation with a subpicosecond spin relaxation time. © 2005 The American Physical Society.
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| 3. |
- Buyanova, Irina, 1960-, et al.
(författare)
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Control of spin functionality in ZnMnSe-based structures : Spin switching versus spin alignment
- 2003
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 82:11, s. 1700-
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Tidskriftsartikel (refereegranskat)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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| 4. |
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| 5. |
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| 6. |
- Buyanova, Irina, 1960-, et al.
(författare)
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Exciton Spin Manipulation in ZnMnSe-Based Structures
- 2003
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Konferensbidrag (refereegranskat)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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| 7. |
- Buyanova, Irina, 1960-, et al.
(författare)
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On the spin injection in ZnMnSe/ZnCdSe heterostructures
- 2002
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Konferensbidrag (refereegranskat)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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| 8. |
- Buyanova, Irina, 1960-, et al.
(författare)
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Resonant suppression of exciton spin relaxation in Zn0.96Mn0.04Se/CdSe superlattices
- 2003
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 93:10, s. 7352-
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Tidskriftsartikel (refereegranskat)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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| 9. |
- Buyanova, Irina, 1960-, et al.
(författare)
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Transient Spectroscopy of Optical Spin Injection in ZnMnSe/ZnCdSe Quantum Structures
- 2005
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Ingår i: Journal of Superconductivity. - Journal of Superconductivity and Novel Magnetism, vol. 18 : Springer. - 0896-1107 .- 1572-9605.
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Konferensbidrag (refereegranskat)abstract
- We show, by time-resolved magneto-photoluminescence (PL) spectroscopy in combination with selective laser excitation, that optical polarization of the ZnCdSe spin detector induced by spin injection from the ZnMnSe spin injector persists over a much longer time scale than the lifetime of the ZnMnSe excitons. This finding provides compelling experimental evidence that the dominant mechanism for the observed spin injection in the ZnMnSe/ZnCdSe structures should not be due to injection of the excitonic spins of the diluted magnetic semiconductor (DMS). It is rather due to e.g. a delayed spin injection arising from tunneling of individual carriers or/and trapped spins in ZnMnSe.
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| 10. |
- Buyanova, Irina, 1960-, et al.
(författare)
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Tunable laser spectroscopy of spin injection in ZnMnSe/ZnCdSe quantum structures
- 2002
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 81:12, s. 2196-
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Tidskriftsartikel (refereegranskat)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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