| 1. |
- 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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| 2. |
- Ivanov, SV, et al.
(författare)
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Plasma-assisted MBE growth and characterization of InN on sapphire
- 2004
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248 .- 1873-5002. ; 269:1
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Tidskriftsartikel (refereegranskat)abstract
- We report on a close correlation between the growth conditions of InN/Al2O3 (0 0 0 1) epilayers grown by plasma-assisted molecular beam epitaxy (MBE), their optical properties in the IR range, and the In clustering in the layers. High-spatial resolution techniques, namely micro-cathodoluminesesence, back-scattered electron imaging and energy dispersive X-ray analysis, were used to establish this correlation. The In-rich growth conditions, achieved by increasing either the growth temperature or the effective In/N flux ratio, causes the In clustering in InN, responsible in our samples for the 0.7-0.8 eV luminescence and IR optical absorption. Growth under In/N = 1: 1 conditions slightly shifted to the N-rich side generally produces InN layers without visible In clusters, having an optical absorption edge around 1.4 eV. A possible mechanism of In cluster formation is suggested on the basis of thermodynamic considerations for InN MBE growth. (C) 2004 Elsevier B.V. All rights reserved.
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| 3. |
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| 4. |
- 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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| 5. |
- Shubina, Tatiana, et al.
(författare)
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Narrow-line excitonic photoluminescence in GaN/AlxGa1-xN quantum well structures with inversion domains
- 2003
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 67:24, s. 241306-
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Tidskriftsartikel (refereegranskat)abstract
- Microphotoluminescence studies reveal strong and narrow lines of similar to1-meV minimal width in GaN/AlxGa1-xN quantum well (QW) structures having inversion domains (IDs). These narrow lines coexist in the spectra with broad (10-15 meV) peaks. The features of both kinds are characteristic for intersections of the IDs with QWs, which provide either three- or one-dimensional carrier confinement, depending on both the ID diameter and well width.
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| 6. |
- Shubina, Tatiana, et al.
(författare)
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Optical properties of InN with stoichoimetry violation and indium clustering
- 2005
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Ingår i: Physica Status Solidi (a) applications and materials science. - : Wiley. - 1862-6300 .- 1862-6319. ; 202:3, s. 377-382
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate that nonstoichiometry is one of the main reason of strong deviation of the InN optical gap in the 0.7-2 eV range, with N/In < 1 and N/In > 1 corresponding to the lower and higher energies, respectively. The phenomenon is discussed in terms of atomic orbital energies, which are strongly different for indium and nitrogen, therefore both excess atom incorporation and elimination could change the optical gap. We estimate such trends using the approximation of the empirical nearest-neighbor tight binding theory. It is also demonstrated that resonant absorption in In-enriched regions is an additional factor lowering an effective absorption edge.
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