| 1. |
- Zhao, QX, et al.
(författare)
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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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Ingår i: Applied Physics Letters. - : American Institute of Physics. - 0003-6951 .- 1077-3118. ; 86:12
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Tidskriftsartikel (refereegranskat)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.
(författare)
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Effects of nitrogen incorporation on the properties of GaInNAs/GaAs quantum well structures
- 2005
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Ingår i: Journal of Applied Physics. - : American Institute of Physics. - 0021-8979 .- 1089-7550. ; 97:7
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Tidskriftsartikel (refereegranskat)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.
(författare)
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Nitrogen incorporation in GaNas layers grown by molecular beam epitaxy
- 2006
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 89:3, s. 31907-1-31907-3
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Tidskriftsartikel (refereegranskat)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.
(författare)
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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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Ingår i: Physics Letters A. - : Elsevier Science B.V., Amsterdam.. - 0375-9601 .- 1873-2429. ; 341:04-Jan, s. 297-302
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Tidskriftsartikel (refereegranskat)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. |
- Fu, Ying, et al.
(författare)
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Energy band structure and spectral gain characteristics of dilute-nitride zinc blende InGaNAs quantum wells embedded in GaAs and GaNAs barriers
- 2006
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 100:7
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Tidskriftsartikel (refereegranskat)abstract
- The spectral gain characteristics of dilute-nitride zinc blende InxGa1-xNyAs1-y quantum wells embedded in GaNy1As1-y1 barriers have been investigated experimentally and theoretically. Two samples, both with the gain peak at 1300 nm, were studied for comparison. One has a high nitrogen concentration in the quantum well with the surrounding barriers being pure GaAs. The other has a lower and uniform nitrogen concentration in the quantum well and the barriers (GaNAs barriers). Measurements show the redshift of the gain peak induced by the incorporation of nitrogen and difference in the spectral gain characteristics. The energy band structures and spectral gain characteristics are analyzed theoretically using the standard eight-band k center dot p theory. It is shown that the introduction of nitrogen atoms in the GaAs barriers reduces the barrier height for the central quantum well so that the energy sublevels in the conduction band becomes condensed. The condensation of the conduction-band energy sublevels reduces the peak gain and makes the gain spectrum narrower, in agreement with measurements.
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| 6. |
- Wang, Shu Min, 1963, et al.
(författare)
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Metamorphic InGaAs quantum wells for light emission at 1.3-1.6 μm
- 2007
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 515:10, s. 4348-4351
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Tidskriftsartikel (refereegranskat)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.
(författare)
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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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Ingår i: Semiconductor Science and Technology. - : IOP Publishing. - 0268-1242 .- 1361-6641. ; 23:12, s. 125002-
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Tidskriftsartikel (refereegranskat)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.
(författare)
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Growth and characterization of GaInNAs by molecular beam epitaxy using a nitrogen irradiation method
- 2009
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Ingår i: JOURNAL OF CRYSTAL GROWTH. - : Elsevier BV. - 0022-0248. ; 311:7, s. 1723-1727
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Tidskriftsartikel (refereegranskat)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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