| 31. |
- Terentev, Ya. V., et al.
(författare)
-
Semimagnetic ZnMnSe/CdSe Fractional Monolayer Superlattice as an Injector of Spin-Polarized Carriers
- 2002
-
Ingår i: Physica status solidi. B, Basic research. - 0370-1972 .- 1521-3951. ; 229:2, s. 765-768
-
Tidskriftsartikel (refereegranskat)abstract
- We report on effective injection of spin-oriented carriers from a semimagnetic semiconductor structure to a non-magnetic ZnCdSe/ZnSe quantum well (QW). A short-period ZnMnSe/CdSe fractional monolayer superlattice was used as a spin injector. The carriers are photo-generated in the semimagnetic region, spin-polarized via the effect of giant Zeeman splitting and then injected into the non-magnetic QW. The spin injection efficiency was estimated by circular polarization measurements of recombination emission from the QW. The maximal detected degree of the spin polarization is about 25%.
|
|
| 32. |
- Toropov, A.A., et al.
(författare)
-
Density-dependent dynamics of exciton magnetic polarons in ZnMnSe/ZnSSe type-II quantum wells
- 2006
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : APS. - 1098-0121 .- 1550-235X. ; 73:24, s. 245335-
-
Tidskriftsartikel (refereegranskat)abstract
- We report on time-resolved photoluminescence studies of exciton dynamics in a ZnMnSe/ZnSSe type-II quantum well. Strong separation of the electrons, confined to the nonmagnetic semiconductor ZnSSe, and holes, confined to the diluted magnetic semiconductor ZnMnSe, results in an exciton lifetime exceeding 3 ns. Two excitonic emission lines are observed in this structure at low temperatures. The lower-energy line was associated with the formation of an exciton magnetic polaron (EMP), whereas the higher-energy line was attributed to the emission of nonmagnetically localized excitons. The intensity of the EMP line was found to saturate at a relatively low density of photoexcited carriers well below the exciton Mott density. This behavior evidences a limited density of sites where the hole localization radius is small enough to ensure the fast formation of EMP's with a noticeable binding energy. © 2006 The American Physical Society.
|
|
| 33. |
- Toropov, A.A., et al.
(författare)
-
Dynamics of excitons near the mobility edge in CdSe/ZnSe superlattices
- 2000
-
Ingår i: Journal of Crystal Growth. - 0022-0248 .- 1873-5002. ; 214, s. 806-809
-
Tidskriftsartikel (refereegranskat)abstract
- The dynamics properties of hot excitons near the effective excitonic mobility edge are investigated in a CdSe/ZnSe superlattice structure where thermalized luminescence of localized excitons is strongly suppressed due to tunneling towards the attached deeper ZnCdSe quantum well. Time-resolved selective-excitation luminescence measurements reveal a rather complicated relaxation behavior involving fast (20-30 ps) acoustical-phonon-assisted selective occupation of states located close to the mobility edge.
|
|
| 34. |
|
|
| 35. |
- Toropov, A.A., et al.
(författare)
-
Magneto-photoluminescence studies of diluted magnetic semiconductor type-II quantum wells ZnMnSe/ZnSSe
- 2003
-
Ingår i: Proceedings of the International Conference on Superlattices, Nano-structures and Nano-devices ICSNN 2002 o-structures and Nano-devices ICSNN 2002. ; , s. 352-354
-
Konferensbidrag (refereegranskat)abstract
- Magneto-photoluminescence (PL) has been studied in type II Zn1-xMnxSe/ZnSySe1-y multiple quantum wells (QWs) with the Mn content x between 0.03 and 0.15. Two PL lines are observed in the samples with x equal to 0.05 and 0.15. The lines are attributed to the excitons of two different types, coexisting in the QWs. At least one of them is associated with the formation of an exciton magnetic polaron. © 2002 Elsevier Science B.V. All rights reserved.
|
|
| 36. |
- Toropov, A. A., et al.
(författare)
-
ZnMnSe/ZnSSe Type-II semimagnetic superlattices : Growth and magnetoluminescence properties
- 2002
-
Ingår i: Semiconductors (Woodbury, N.Y.). - : Pleiades Publishing Ltd. - 1063-7826 .- 1090-6479. ; 36:11, s. 1288-1293
-
Tidskriftsartikel (refereegranskat)abstract
- A ZnSSe/ZnMnSe type-II semimagnetic superlattice was pseudomorphically grown via molecular beam epitaxy on a GaAs substrate. The superlattice-layer thicknesses and compositions were chosen so that compressive strains in the ZnMnSe layer compensated tensile strains in the ZnSSe layer. The photoluminescence spectra in an external magnetic field demonstrate the effect of giant Zeeman splitting of an exciton. Simulation of the luminescence-line shift in a magnetic field allowed us to determine more accurately the band offsets at the ZnSSe/ZnMnSe interface.
|
|
| 37. |
- Buyanova, Irina, 1960-, et al.
(författare)
-
Control of spin functionality in ZnMnSe-based structures : Spin switching versus spin alignment
- 2003
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 82:11, s. 1700-
-
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.
|
|
| 38. |
|
|
| 39. |
- Buyanova, Irina, 1960-, et al.
(författare)
-
Exciton Spin Manipulation in ZnMnSe-Based Structures
- 2003
-
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.
|
|
| 40. |
- Buyanova, Irina, 1960-, et al.
(författare)
-
Resonant suppression of exciton spin relaxation in Zn0.96Mn0.04Se/CdSe superlattices
- 2003
-
Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 93:10, s. 7352-
-
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.
|
|
