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| 2. |
- Hsiao, Ching-Lien, et al.
(author)
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Composition tunable Al1-xInxN nanorod arrays grown by ultra-high-vacuum magnetron sputter epitaxy
- 2011
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Other publication (other academic/artistic)abstract
- Self-assembled ternary Al1-xInxN nanorod arrays with variable In concentration, 0.10 ≤ x ≤ 0.32 have been realized onto c-plane sapphire substrates by ultra-high-vacuum magnetron sputter epitaxy with Ti0.21Zr0.79N or VN seed layers assistance. The formation of nanorods was very sensitive to the applied seed layer. Without proper seed layer assistance a continuous Al1-xInxN film was grown. The nanorods exhibit hexagonal crosssections with preferential growth along the c axis. A coaxial rod structure with higher In concentration in the core was observed by (scanning) transmission electron microscopy in combination with low-loss electron energy loss spectroscopy and energy dispersive xray spectroscopy. 5 K cathodoluminescence spectroscopy of Al0.86In0.14N nanorods revealed band edge emission at ~5.46 eV, which was accompanied by a strong defectrelated emission at ~ 3.38 eV.
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| 3. |
- Hsiao, Ching-Lien, et al.
(author)
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Spontaneous Formation of AlInN Core–Shell Nanorod Arrays by Ultrahigh-Vacuum Magnetron Sputter Epitaxy
- 2011
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In: Applied Physics Express. - : Japan Society of Applied Physics. - 1882-0786. ; 4:115002
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Journal article (peer-reviewed)abstract
- The spontaneous formation of AlInN core–shell nanorod arrays with variable In concentration has been realized by ultrahigh-vacuum magnetron sputter epitaxy with Ti0.21Zr0.79N or VN seed layer assistance. The nanorods exhibit hexagonal cross sections with preferential growth along the c-axis. A core–shell rod structure with a higher In concentration in the core was observed by (scanning) transmission electron microscopy in combination with low-loss electron energy loss spectroscopy and energy dispersive X-ray spectroscopy. 5 K cathodoluminescence spectroscopy of Al0.86In0.14N nanorods revealed band edge emission at ∼5.46 eV, which was accompanied by a strong defect-related emission at ∼3.38 eV
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| 4. |
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| 5. |
- Amloy, Supaluck, et al.
(author)
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Excitons and biexcitons in InGaN quantum dot like localization centers
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Other publication (other academic/artistic)abstract
- Indium segregation in a narrow InGaN single quantum well creates quantum dot (QD) like exciton localization centers. Cross section transmission electron microscopy reveals varying shapes and lateral sizes in the range ~1-5 nm of the QD-like features, while scanning near field optical microscopy demonstrates a highly inhomogeneous spatial distribution of optically active individual localization centers. Microphotoluminescence spectroscopy confirms the spectrally inhomogeneous distribution of localization centers, in which the exciton and the biexciton related emissions from single centers of varying geometry could be identified by means of excitation power dependencies. Interestingly, the biexciton binding energy (Ebxx) was found to vary from center to center, between 3 to -22 meV, in correlation with the exciton emission energy. Negative binding energies justify the three-dimensional quantum confinement, which confirms QD-like properties of the localization centers.! The observed energy correlation is proposed to be understood as variations of the lateral extension of the confinement potential, which would yield smaller values of Ebxx for reduced lateral extension and higher exciton emission energy. The proposed relation between lateral extension and Ebxx is further supported by the exciton and the biexciton recombination lifetimes of a single QD, which suggest a lateral extension of merely ~3 nm for a QD with strongly negative Ebxx = -15.5 meV.
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| 6. |
- Amloy, Supaluck, et al.
(author)
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Excitons and biexcitons in InGaN quantum dot like localization centers
- 2014
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In: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 25:49, s. 495702-
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Journal article (peer-reviewed)abstract
- Indium segregation in a narrow InGaN single quantum well creates quantum dot (QD) like exciton localization centers. Cross-section transmission electron microscopy reveals varying shapes and lateral sizes in the range ∼1–5 nm of the QD-like features, while scanning near field optical microscopy demonstrates a highly inhomogeneous spatial distribution of optically active individual localization centers. Microphotoluminescence spectroscopy confirms the spectrally inhomogeneous distribution of localization centers, in which the exciton and the biexciton related emissions from single centers of varying geometry could be identified by means of excitation power dependencies. Interestingly, the biexciton binding energy (Ebxx) was found to vary from center to center, between 3 to −22 meV, in correlation with the exciton emission energy. Negative binding energies are only justified by a three-dimensional quantum confinement, which confirms QD-like properties of the localization centers. The observed energy correlation is proposed to be understood as variations of the lateral extension of the confinement potential, which would yield smaller values of Ebxx for reduced lateral extension and higher exciton emission energy. The proposed relation between lateral extension and Ebxx is further supported by the exciton and the biexciton recombination lifetimes of a single QD, which suggest a lateral extension of merely ∼3 nm for a QD with strongly negative Ebxx = −15.5 meV.
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| 7. |
- Chen, Yen-Ting, et al.
(author)
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Nucleation of single GaN nanorods with diameters smaller than 35 nm by molecular beam epitaxy
- 2013
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In: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 103:20, s. 203108-
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Journal article (peer-reviewed)abstract
- Nucleation mechanism of catalyst-free GaN nanorod grown on Si(111) is investigated by the fabrication of uniform and narrow (andlt; 35 nm) nanorods without a pre-defined mask by molecular beam epitaxy. Direct evidences show that the nucleation of GaN nanorods stems from the sidewall of the underlying islands down to the Si(111) substrate, different from commonly reported ones on top of the island directly. Accordingly, the growth and density control of the nanorods is exploited by a "narrow-pass" approach that only narrow nanorod can be grown. The optimal size of surrounding non-nucleation area around single nanorod is estimated as 88 nm.
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| 8. |
- Ding Yuan, Chen, 1991, et al.
(author)
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Impact of in situ NH3 pre-treatment of LPCVD SiN passivation on GaN HEMT performance
- 2022
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In: Semiconductor Science and Technology. - : IOP Publishing. - 1361-6641 .- 0268-1242. ; 37:3
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Journal article (peer-reviewed)abstract
- The impact on the performance of GaN high electron mobility transistors (HEMTs) of in situ ammonia (NH3) pre-treatment prior to the deposition of silicon nitride (SiN) passivation with low-pressure chemical vapor deposition (LPCVD ) is investigated. Three different NH3 pre-treatment durations (0, 3, and 10 min) were compared in terms of interface properties and device performance. A reduction of oxygen (O) at the interface between SiN and epi-structure is detected by scanning transmission electron microscopy (STEM )-electron energy loss spectroscopy (EELS) measurements in the sample subjected to 10 min of pre-treatment. The samples subjected to NH3 pre-treatment show a reduced surface-related current dispersion of 9% (compared to 16% for the untreated sample), which is attributed to the reduction of O at the SiN/epi interface. Furthermore, NH3 pre-treatment for 10 min significantly improves the current dispersion uniformity from 14.5% to 1.9%. The reduced trapping effects result in a high output power of 3.4 W mm(-1) at 3 GHz (compared to 2.6 W mm(-1) for the untreated sample). These results demonstrate that the in situ NH3 pre-treatment before LPCVD of SiN passivation is critical and can effectively improves the large-signal microwave performance of GaN HEMTs.
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| 9. |
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| 10. |
- Giang, Kok Wai, 1984, et al.
(author)
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Long-term risk of stroke and myocardial infarction in middle-aged men with a hypertensive response to exercise : a 44-year follow-up study
- 2021
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In: Journal of Hypertension. - : Wolters Kluwer. - 0263-6352 .- 1473-5598. ; 39:3, s. 503-510
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Journal article (peer-reviewed)abstract
- Introduction: Data on the prognostic value of hypertensive response to exercise in cardiovascular disease are limited. The aim was to determine whether SBP reactions during exercise have any prognostic value in relation to the long-term risk of stroke and myocardial infarction (MI).Patients and methods: A representative cohort of men from Gothenburg, Sweden, born in 1913, who performed a maximum exercise test at age 54 years, (n = 604), was followed-up for a maximum of 44 years with regard to stroke and MI. Results: Among the 604 men, the mean resting and maximum SBP was 141.5 (SD 18.8) and 212.1 (SD 24.6) mmHg, respectively. For maximum SBP, the risk of stroke increased by 34% (hazard ratio 1.34, 95% confidence interval 1.11-1.61) per 1-SD increase, while no risk increase was observed for MI. The highest risk of stroke among blood pressure groups was observed among men with a resting SBP of at least 140 mmHg and a maximum SBP of at least 210 mmHg with an hazard ratio of 2.09 (95% confidence interval 1.29-3.40), compared with men with a resting SBP of less than 140 mmHg and a maximum SBP of less than 210 mmHg, independent of smoking, blood glucose, cholesterol and BMI.Conclusion: Among middle-aged men with high resting and maximum blood pressure during maximum exercise workload, an increased risk of stroke was observed but not for MI. Further studies with larger sample sizes are needed to investigate the underlying mechanisms of the increased risk of stroke among individuals with hypertensive response to exercise.
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