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- Adham, Kristi
(författare)
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Growth and Characterization of Core-Branch Nanowire Structures
- 2022
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis investigates growth of III – V semiconductor nanowire (NW) arrays, in a core- branch architecture, with the aim to develop diffusion driven light emitting diodes (LED) on NWs. Diffusion driven LEDs are based on the concept of decoupling the active region from the p-n junction. The carriers are injected by diffusion in the active region, because of the bandgap difference between the pn junction and the active region. This concept can be used in NW structures where tree structures are grown with high bandgap cores and low bandgap branches. The small diameter of the branches facilitates light extraction and removes the limitation of total internal reflection. The first part of the thesis focuses on studying the deposition parameters of Au particles on the sidewalls of the core NWs. These particles act as catalysts for branch growth. The second part of the thesis focuses on the growth of branches from homostructures (InP-InP) and heterostructures (InGaP-InGaP) where the Ga content in the core is higher than in the branches. We demonstrate high density branch growth distributed along the entire core length. Finally, we present some results from photoluminescence measurements in heterostructure core-branch NWs. The results presented in this thesis are intended to contribute to the development of a new and promising LED architecture.
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| 2. |
- Adham, Kristi, et al.
(författare)
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Growth of branched nanowires via solution-based Au seed particle deposition
- 2023
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Ingår i: Materials Research Express. - 2053-1591. ; 10:8
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Tidskriftsartikel (refereegranskat)abstract
- Nanowires offer unprecedented flexibility as nanoscale building blocks for future optoelectronic devices, especially with respect to nanowire solar cells and light-emitting diodes. A relatively new concept is that of charge carrier diffusion-induced light-emitting diodes, for which nanowires offer an interesting architecture by use of particle-assisted core-branch growth. The branches should be homogenously distributed along the cores. However, most deposition techniques, such as aerosol particle deposition, mainly yield particles at the nanowire tips for dense nanowire arrays. In this study, we demonstrate a liquid-based approach for homogeneously distributed formation of catalytic Au particles on the core nanowire sidewalls which is cost and time-efficient. Subsequently, we demonstrate the synthesis of dispersed nanowire branches. We show that by changing the deposition parameters, we can tune the number of branches, their dimensions, and their growth direction.
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| 3. |
- Jeddi Abdarloo, Hossein, Doktorand, 1992-, et al.
(författare)
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Enhanced LWIR response of InP/InAsP quantum discs-in-nanowire array photodetectors by photogating and ultra-thin ITO contacts
- 2024
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Ingår i: Nanotechnology. - Bristol : Institute of Physics Publishing (IOPP). - 0957-4484 .- 1361-6528. ; 35:21, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- Here we report on an experimental and theoretical investigation of the long-wavelength infrared (LWIR) photoresponse of photodetectors based on arrays of three million InP nanowires with axially embedded InAsP quantum discs. An ultra-thin top indium tin oxide contact combined with a novel photogating mechanism facilitates an improved LWIR normal incidence sensitivity in contrast to traditional planar quantum well photodetectors. The electronic structure of the quantum discs, including strain and defect-induced photogating effects, and optical transition matrix elements were calculated by an 8-band k center dot p simulation along with solving drift-diffusion equations to unravel the physics behind the generation of narrow linewidth intersubband signals observed from the quantum discs © 2024 The Author(s). Published by IOP Publishing Ltd.
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| 4. |
- Jeddi Abdarloo, Hossein, Doktorand, 1992-, et al.
(författare)
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Spectrally Tunable Broadband Gate-All-Around InAsP/InP Quantum Discs-in-Nanowire Array Phototransistors with a High Gain-Bandwidth Product
- 2023
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Ingår i: ACS Photonics. - Washington, DC : American Chemical Society (ACS). - 2330-4022. ; 10:6, s. 1748-1755
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Tidskriftsartikel (refereegranskat)abstract
- High-performance broadband photodetectors offering spectral tunability and a high gain-bandwidth product are crucial in many applications. Here, we report on a detailed experimental and theoretical study of three-terminal phototransistors comprised of three million InP nanowires with 20 embedded InAsP quantum discs in each nanowire. A global, transparent ITO gate all around the nanowires facilitates a radial control of the carrier concentration by more than two orders of magnitude. The transfer characteristics reveal two different transport regimes. In the subthreshold region, the photodetector operates in a diffusion mode with a distinct onset at the bandgap of InP. At larger gate biases, the phototransistor switches to a drift mode with a strong contribution from the InAsP quantum discs. Besides an unexpected spectral tunability, the detector exhibits a state-of-the-art responsivity, reaching around 100 A/W (638 nm/20 μW) @ VGS = 1.0 V/VDS = 0.5 V with a gain-bandwidth product of around 1 MHz, in excellent agreement with a comprehensive real-device model. © 2023 The Authors. Published by American Chemical Society.
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