| 1. |
- Shubina, Tatiana, et al.
(författare)
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Intrinsic electric fields in N-polarity GaN/AlxGa1-xN quantum wells with inversion domains
- 2003
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 67:19
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Tidskriftsartikel (refereegranskat)abstract
- GaN/AlGaN quantum wells (QWs) of dominant N polarity with inversion domains (IDs), grown by molecular-beam epitaxy, have been studied. Two-band photoluminescence (PL), with the lower-energy band and an additional absorption edge related to the IDs, is observed in these QWs due to a difference in strain, electric field, and well width in the regions of different polarities. A time-resolved PL study reveals additionally strong inhomogeneity of the electric fields among the IDs. The intrinsic electric fields in the structures are relatively small-their maximal estimated value of 180 kV/cm is among the lowest ever reported. The low-scale electric fields indicate likely polarization deterioration in the N-polarity structures. These conditions are favorable for bright PL up to room temperature in 8-9-nm-wide wells.
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| 2. |
- Shubina, Tatiana, et al.
(författare)
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Nanometric-scale fluctuations of intrinsic electric fields in GaN/AlGaN quantum wells with inversion domains
- 2002
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Ingår i: Physica status solidi. B, Basic research. - 0370-1972 .- 1521-3951. ; 234:3, s. 919-923
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Tidskriftsartikel (refereegranskat)abstract
- Strain and electric field fluctuations in regions of different polarities in GaN/AlGaN quantum well (QW) structures of dominant N-polarity with inversion domains (IDs) split the photoluminescence (PL) emission into two bands. Micro-PL and time-resolved PL studies reveal strong inhomogeneity of the array of the IDs, where essential parameters, such as strain, electric fields, and sizes are fluctuating quantities. We demonstrate also that the ID formation decreases the intrinsic electric field magnitudes.
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| 3. |
- Chen, Weimin, et al.
(författare)
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Exciton spin relaxation in diluted magnetic semiconductor Zn1-xMnxSe/CdSe superlattices : Effect of spin splitting and role of longitudinal optical phonons
- 2003
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 67:12
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Tidskriftsartikel (refereegranskat)abstract
- Exciton spin relaxation in diluted magnetic semiconductor (DMS) structures based on ZnMnSe is closely examined as a function of exciton spin splitting in an external magnetic field. A drastic increase in spin relaxation is observed when exciton spin splitting exceeds the longitudinal optical (LO) phonon energy. Direct experimental evidence has been provided from (1) spin injection from the DMS to an adjacent nonmagnetic quantum well that can be modulated by the LO-assisted spin relaxation and (2) hot exciton photoluminescence within the DMS where a spin flip is accompanied by the emission of one LO phonon.
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| 4. |
- Shubina, Tatiana, et al.
(författare)
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Interface effects in type-II CdSe/BeTe quantum dots
- 2002
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Ingår i: Physica status solidi. B, Basic research. - 0370-1972 .- 1521-3951. ; 229:1, s. 489-492
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Tidskriftsartikel (refereegranskat)abstract
- We report on optical and structural studies of the interface symmetry in CdSe/BeTe multiple-layer structures containing self-assembled quantum dots. Temperature and decay behavior of the broad photoluminescence (PL) band is consistent with the type-II transitions involving deeply localized electron states. Large linear in-plane polarization of the PL (up to 80%) is observed, implying the C-2v (or lower) symmetry of the individual places of the electron localization.
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| 5. |
- Shubina, Tatiana, et al.
(författare)
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Micro-photoluminescence spectroscopy of exciton-polaritons in GaN with the wave vector k normal to the c-axis
- 2001
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Ingår i: Physica status solidi. B, Basic research. - 0370-1972 .- 1521-3951. ; 228:2, s. 481-484
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Tidskriftsartikel (refereegranskat)abstract
- We report on polarized micro-photoluminescence (mu -PL) and micro-reflectance (mu -R) studies of GaN layers grown by HVPE. A strong pi -polarized component in the vicinity of A exciton is observed in the mu -PL and attributed as a mixture of a bound B exciton, dominating at low temperature, and scattered A exciton-polariton states prevailing at higher temperatures. Temperature variation of exciton energies in the mu -R spectra reveals strain-induced difference between the top surface and the cleaved edges.
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| 6. |
- Shubina, Tatiana, et al.
(författare)
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Peculiarities of exciton-polaritons in GaN at different polarizations studied by mu-photoluminescence spectroscopy
- 2002
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Ingår i: Physica status solidi. A, Applied research. - 0031-8965 .- 1521-396X. ; 190:1, s. 205-211
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Tidskriftsartikel (refereegranskat)abstract
- We report on polariton properties in high quality thick GaN grown by hydride vapor phase epitaxy on c-sapphire. A strong fine is observed in the vicinity of the A exciton in T-polarization (k perpendicular to c, E parallel to the c-axis) by micro-photoluminescence (mu-PL). Comparison of the mu-PL and mu-reflectance spectra confirms the internal origin of the polariton emission. In the samples with low density of residual donors the enhancement of the a-polarized component is induced mostly by interbranch scattering which occurs, possibly., due to the complex structure of the exciton-polariton branches at k perpendicular to c. The Gamma(1)-Gamma(5) exciton splitting in the C band is determined by the mu-reflectance as similar to1 meV.
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| 7. |
- Shubina, TV, et al.
(författare)
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Polarized microphotoluminescence and reflectance spectroscopy of GaN with k perpendicular to c : Strongly pi-polarized line near the A exciton
- 2002
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 65:7
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Tidskriftsartikel (refereegranskat)abstract
- Polarized microphotoluminescence (mu-PL) and reflectivity studies of thick wurtzite GaN grown by hydride vapor phase epitaxy on c sapphire are performed with the light vector k both normal to the c axis (kperpendicular toc) and parallel to it. A strong PL peak is found in the vicinity of the A exciton in pi polarization (kperpendicular toc, E parallel to the c axis). in apparent contradiction to the selection rules. The pi-polarized component exceeds in intensity the sigma-polarized one up to similar to50 K. Power- and temperature-dependent measurements of both no-phonon and longitudinal optical phonon-assisted (monitoring the real density of exciton states) mu-PL reveal the complex nature of the pi-polarized PL line near the A exciton. At low temperatures the pi-component involves a bound B exciton contribution, while at higher temperatures contributions of scattered A exciton states become appreciable, The enhancement of the pi-polarized component is attributed to the complex structure of the exciton-polariton branches for kperpendicular toc. Temperature-dependent mu-PL and reflectance spectroscopies reveal additionally a difference in the optical properties between the sample regions at the top surface and the cleaved edges, tentatively explained as induced by different strains in these regions.
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| 8. |
- Toropov, AA, et al.
(författare)
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Temperature-dependent polarized luminescence of exciton polaritons in a ZnO film
- 2005
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Ingår i: Physica Status Solidi (a) applications and materials science. - : Wiley. - 1862-6300 .- 1862-6319. ; 202:3, s. 392-395
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Tidskriftsartikel (refereegranskat)abstract
- We report on the studies of linearly polarized photoluminescence (PL) in a (0001) oriented ZnO epitaxial film, grown by metal organic chemical vapor deposition on a GaN template. The emission of mixed longitudinal-transverse exciton polariton modes was observed up to 130 K that evidences polaritonic nature of the excitonic spectrum up to this elevated temperature.
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