| 1. |
- Zhao, QX, et al.
(author)
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Effect of growth temperature and post-growth thermal annealing on carrier localization and deep level emissions in GaNAs/GaAs quantum well structures
- 2005
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In: Applied Physics Letters. - : American Institute of Physics. - 0003-6951 .- 1077-3118. ; 86:12
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Journal article (peer-reviewed)abstract
- We report results from investigation of the optical properties of GaNAs/GaAs quantum well structures. The structures were grown by molecular-beam epitaxy at different temperatures, and subsequently postgrowth thermal treatments at different temperature were performed. The results show that the carrier localization is smaller in a structure grown at a temperature of 580 degrees C in comparison with a structure grown at 450 degrees C. Both structures also show a broaden deep level emission band. Furthermore, the deep level emission band and the carrier localization effect can be removed by thermal annealing at 650 degrees C in the structure grown at 450 degrees C. The structure quality and radiative recombination efficiency are significantly improved after annealing. However, annealing under the same condition has a negligible effect on the structure grown at 580 degrees C. (C) 2005 American Institute of Physics.
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| 2. |
- Zhao, QX, et al.
(author)
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Effects of nitrogen incorporation on the properties of GaInNAs/GaAs quantum well structures
- 2005
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In: Journal of Applied Physics. - : American Institute of Physics. - 0021-8979 .- 1089-7550. ; 97:7
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Journal article (peer-reviewed)abstract
- We report results from theoretical and experimental investigations of GaInNAs/GaAs quantum well structures. Optical transition energies for samples with different In and N concentrations were determined by photoluminescence measurements. The results show that the reduction of the ground-state transition energy by the introduction of N decreases with increasing In concentration. The experimental data are compared with calculations using the effective-mass approximation. Modifications of the band-gap energy due to N incorporation were accounted for using the two-level repulsion model. Proper effective-mass and band offset values, based on recent experimental work, were used. Calculated and measured transition energies show good agreement. The critical thickness, lattice constant, strain, and optical transition energies are discussed for GaInNAs/GaAs quantum well structures tuned for emission at 1.3 and 1.55 mu m, in particular. Such a simple model, within the effective-mass approximation, is a very useful guide for device design. (C) 2005 American Institute of Physics.
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| 3. |
- Zhao, Qingxiang, 1962, et al.
(author)
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Nitrogen incorporation in GaNas layers grown by molecular beam epitaxy
- 2006
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 89:3, s. 31907-1-31907-3
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Journal article (peer-reviewed)abstract
- GaNAs/GaAs quantum wells with high N concentrations, grown by molecular beam epitaxy, have been investigated by secondary-ion mass spectrometry (SIMS), high resolution x-ray diffraction (XRD), and photoluminescence (PL) measurements. The substitutional N concentration in an 18 nm thick strained GaNAs layer varies from 1.4% to 5.9% when the growth rate is reduced from 1 to 0.2 μm/h. By further reducing the growth rate, more N can be incorporated but relaxation occurs. Both the total N concentration, deduced from SIMS measurements, and the substitutional N concentration, deduced from XRD measurements, increase with reduced growth rate. By comparing the SIMS and XRD results, we found that a large amount of N was not in substitutional position when the substitutional N concentration is high (≫4%). The experimental results also show that there is no detectable change of total and substitutional N concentrations, within the instrument resolutions, after rapid thermal annealing at 700 °C for 30 s. However, PL measurements show a strong blueshift of the emission wavelength after annealing and the PL intensity increases by more than one order of magnitude.
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| 4. |
- Zhao, QX, et al.
(author)
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Radiative recombination of localized excitons and mobility edge excitons in GaInNAs/GaAs quantum wells with strong carrier localization
- 2005
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In: Physics Letters A. - : Elsevier Science B.V., Amsterdam.. - 0375-9601 .- 1873-2429. ; 341:04-Jan, s. 297-302
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Journal article (peer-reviewed)abstract
- The radiative recombination in InxGa1-xN0.01As0.99/GaAs quantum well structures exhibiting strong carrier localization was investigated by optical spectroscopy. For In-concentration from 0 to 30%, the results indicate that the degree of carrier localization decreases with increasing In-concentration. At temperatures below 100 K, the mobility edge excitons as well as localized excitons are identified and their transitions energies strongly depend on the excitation intensity. At elevated temperatures the localized excitons become quenched. The temperature dependence of the photoluminescence emission energy shows different behaviors at different excitation intensities.
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| 5. |
- Kakanakova-Georgieva, Anelia, 1970-, et al.
(author)
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Mg-doped Al0.85Ga0.15N layers grown by hot-wall MOCVD with low resistivity at room temperature
- 2010
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In: PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS. - : John Wiley and Sons, Ltd. - 1862-6254 .- 1862-6270. ; 4:11, s. 311-313
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Journal article (peer-reviewed)abstract
- We report on the hot-wall MOCVD growth of Mg-doped AlxGa1-xN layers with an Al content as high as x similar to 0.85. After subjecting the layers to post-growth in-situ annealing in nitrogen in the growth reactor, a room temperature resistivity of 7 k Omega cm was obtained indicating an enhanced p-type conductivity compared to published data for AlxGa1-xN layers with a lower Al content of x similar to 0.70 and a room temperature resistivity of about 10 k Omega cm. It is believed that the enhanced p-type conductivity is a result of reduced compensation by native defects through growth conditions enabled by the distinct hot-wall MOCVD system.
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| 6. |
- Wang, Shu Min, 1963, et al.
(author)
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Metamorphic InGaAs quantum wells for light emission at 1.3-1.6 μm
- 2007
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In: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 515:10, s. 4348-4351
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Journal article (peer-reviewed)abstract
- Metamorphic InGaAs quantum well structures grown on GaAs reveal strong light emission at 1.3-1.6 μm, smooth surface with an average roughness below 2 nm and good rectifying I-V characteristics. Dark line defects are found in the QW. Post growth thermal annealing further improves the luminescence efficiency but does not remove those dark line defects. Some challenges of epitaxial growth using this method for laser applications are discussed. © 2006 Elsevier B.V. All rights reserved.
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| 7. |
- Zhao Ternehäll, Huan, 1982, et al.
(author)
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Comparison of optical and structural quality of GaIn(N) As analog and digital quantum wells grown by molecular beam epitaxy
- 2008
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In: Semiconductor Science and Technology. - : IOP Publishing. - 0268-1242 .- 1361-6641. ; 23:12, s. 125002-
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Journal article (peer-reviewed)abstract
- A set of Ga0.625In0.375(N) As single quantum well (QW) samples with the identical total amounts of Ga and In and QW thicknesses was designed and grown by both the analog and the digital methods using molecular beam epitaxy. The N exposure time in the GaInNAs samples was kept the same. The inter-band gap recombination in the analog and the digital InGaAs QWs appears in a similar transition energy range as a result of In segregation. Temperature-dependent photoluminescence (PL) measurements were performed on the GaInNAs samples. An S-shaped dependence of the transition energy on temperature was observed in the digital GaInNAs QWs but not in the analog GaInNAs QW. Post-growth rapid thermal annealing had remarkably different effects on the PL intensity: an increase for the analog InGaAs QW and for the analog and digital GaInNAs QWs, but a decrease for the digital InGaAs QW with increasing annealing temperature. The GaIn(N) As samples grown by the digital method showed weaker PL intensities and smaller wavelength blue-shifts than the similar samples grown by the analog method. Possible strain relaxation mechanisms are discussed.
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| 8. |
- Zhao Ternehäll, Huan, 1982, et al.
(author)
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Growth and characterization of GaInNAs by molecular beam epitaxy using a nitrogen irradiation method
- 2009
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In: JOURNAL OF CRYSTAL GROWTH. - : Elsevier BV. - 0022-0248. ; 311:7, s. 1723-1727
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Journal article (peer-reviewed)abstract
- We propose an innovative technique, making use of the In segregation effect, referred as the N irradiation method, to enhance In-N bonding and extend the emission wavelength of GaInNAs quantum wells (QWs). After the formation of a complete In floating layer, the growth is interrupted and N irradiation is initiated. The majority of N atoms are forced to bond with In atoms and their incorporation is regulated independently by the N exposure time and the As pressure. The effect of the N exposure time and As pressure on the N incorporation and the optical quality of GaInNAs QWs were investigated. Anomalous photoluminescence (PL) wavelength red shifts after rapid thermal annealing (RTA) were observed in the N-irradiated samples, whereas a normal GaInNAs sample revealed a blue shift. This method provides an alternative way to extend the emission wavelength of GaInNAs QWs with decent optical quality. We demonstrate light emission at 1546 nm from an 11-nm-thick QW, using this method and the PL intensity is similar to that of a 7-nm-thick GaInNAs QW grown at a reduced rate.
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