| 1. |
- Karimi, Mohammad, 1988-, et al.
(author)
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Room-temperature InP/InAsP Quantum Discs-in-Nanowire Infrared Photodetectors
- 2017
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In: Nano letters (Print). - Washington, DC : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 17:6, s. 3356-3362
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Journal article (peer-reviewed)abstract
- The possibility to engineer nanowire heterostructures with large bandgap variations is particularly interesting for technologically important broadband photodetector applications. Here we report on a combined study of design, fabrication, and optoelectronic properties of infrared photodetectors comprising four million n+–i–n+ InP nanowires periodically ordered in arrays. The nanowires were grown by metal–organic vapor phase epitaxy on InP substrates, with either a single or 20 InAsP quantum discs embedded in the i-segment. By Zn compensation of the residual n-dopants in the i-segment, the room-temperature dark current is strongly suppressed to a level of pA/NW at 1 V bias. The low dark current is manifested in the spectrally resolved photocurrent measurements, which reveal strong photocurrent contributions from the InAsP quantum discs at room temperature with a threshold wavelength of about 2.0 μm and a bias-tunable responsivity reaching 7 A/W@1.38 μm at 2 V bias. Two different processing schemes were implemented to study the effects of radial self-gating in the nanowires induced by the nanowire/SiOx/ITO wrap-gate geometry. Summarized, our results show that properly designed axial InP/InAsP nanowire heterostructures are promising candidates for broadband photodetectors. © 2017 American Chemical Society.
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| 2. |
- Lindgren, David, et al.
(author)
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A luminescence study of doping effects in InP-based radial nanowire structures
- 2013
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In: Journal of Physics, Conference Series. - : Institute of Physics Publishing (IOPP). - 1742-6588 .- 1742-6596. ; 471:1
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Journal article (peer-reviewed)abstract
- We have used micro-photo- and cathodo-luminescence at low temperatures to study the effects of sulphur doping in InP and radial InP/InAs/InP structured nanowires. Samples with pure wurtzite crystal structure, with modulated wurtzite/zincblende crystal structure and with different radial InAs growth times were investigated. We observed a doping concentration gradient along the nanowires, the location of segments of different crystal structure and thickness fluctuations on the monolayer scale of the InAs layer.
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| 3. |
- Bi, Zhaoxia, et al.
(author)
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InN quantum dots on GaN nanowires grown by MOVPE
- 2014
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In: physica status solidi (c). - : Wiley. - 1862-6351 .- 1610-1642 .- 1610-1634. ; 11, s. 421-424
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Journal article (peer-reviewed)abstract
- In this work, growth of InN quantum dots (QDs) on GaN nanowires (NWs) by metal-organic vapour phase epitaxy is demonstrated, illustrating the feasibility to combine 0D and 1D structures for nitride semiconductors. Selective area growth was used to generate arrays of c-oriented GaN NWs using Si3N4 as the mask material. In general, InN QDs tend to form at the NW edges between the m-plane side facets, but the QD growth can also be tuned to the side facets by controlling the growth temperature and the growth rate. TEM characterization reveals that I1-type stacking faults are formed in the QDs and originate from the misfit dislocations at the InN/GaN interface. Photoluminescence measurement at 4 K shows that the peak shifts to high energy with reduced dot size. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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| 4. |
- Borgström, Max, et al.
(author)
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Changes in Retinal Thickness and Brain Volume during 6.8-Year Escalating Therapy for Multiple Sclerosis
- 2023
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In: Acta Neurologica Scandinavica. - : WILEY. - 0001-6314 .- 1600-0404. ; 2023
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Journal article (peer-reviewed)abstract
- Background. Different disease-modifying therapies (DMT) for multiple sclerosis (MS) have disparate effects on disability outcomes. Sweden has a leading position globally in initiating high-efficacy DMT instead of escalating DMT from 1(st)-line to high-efficacy DMT. With optical coherence tomography (OCT), retinal changes can be measured at a few micrometer level. OCT has been increasingly applied in diagnosing MS and monitoring disease course and therapeutic effect. Objective. We investigate the effects of 1(st)-line versus high-efficacy DMT for MS on retinal and brain atrophy and on functional outcomes during 6.8 years of escalating DMT. Materials and Methods. In this prospective longitudinal observational study, 18 MS patients were followed up for 6.8 years. Twelve of the patients were untreated at baseline. All patients underwent 1(st)-line DMT for median duration of 2.4 years and then switched to high-efficacy DMT for a median duration of 2.9 years. Findings from neurological examinations, MRI, and OCT measures were registered 2-4 times per year. Results. Ganglion cell-inner plexiform layer (GCIPL) thickness was significantly reduced during 1(st)-line DMT (73.75 mu m, p < 0.01) compared to baseline (76.38 mu m). During high-efficacy DMT, thickness reduction was slower (73.27 mu m, p < 0.05), and MRI contrast-loading lesions vanished (p < 0.01). However, brain parenchymal fraction (BPF) decreased during high-efficacy DMT compared to 1(st)-line DMT. Estimated models showed similar results. Conclusion. GCIPL decline was most profound during 1(st)-line DMT and diminished during high-efficacy DMT. MRI contrast lesions vanished during high-efficacy DMT. However, brain atrophy continued regardless of high-efficacy DMT.
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