| 1. |
- Jain, Vishal, et al.
(author)
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Study of photocurrent generation in InP nanowire-based p(+)-i-n(+) photodetectors
- 2014
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In: Nano Reseach. - Beijing & Berlin/Heidelberg : Springer Science and Business Media LLC. - 1998-0124 .- 1998-0000. ; 7:4, s. 544-552
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Journal article (peer-reviewed)abstract
- We report on electrical and optical properties of p(+)-i-n(+)photodetectors/solar cells based on square millimeter arrays of InP nanowires (NWs) grown on InP substrates. The study includes a sample series where the p(+)-segment length was varied between 0 and 250 nm, as well as solar cells with 9.3% efficiency with similar design. The electrical data for all devices display clear rectifying behavior with an ideality factor between 1.8 and 2.5 at 300 K. From spectrally resolved photocurrent measurements, we conclude that the photocurrent generation process depends strongly on the p(+)-segment length. Without a p(+)-segment, photogenerated carriers funneled from the substrate into the NWs contribute strongly to the photocurrent. Adding a p(+)-segment decouples the substrate and shifts the depletion region, and collection of photogenerated carriers, to the NWs, in agreement with theoretical modeling. In optimized solar cells, clear spectral signatures of interband transitions in the zinc blende and wurtzite InP layers of the mixed-phase i-segments are observed. Complementary electroluminescence, transmission electron microscopy (TEM), as well as measurements of the dependence of the photocurrent on angle of incidence and polarization, support our interpretations.
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| 2. |
- Jeddi Abdarloo, Hossein, Doktorand, 1992-, et al.
(author)
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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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In: Nanotechnology. - Bristol : Institute of Physics Publishing (IOPP). - 0957-4484 .- 1361-6528. ; 35:21, s. 1-7
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Journal article (peer-reviewed)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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| 3. |
- Jeddi Abdarloo, Hossein, Doktorand, 1992-, et al.
(author)
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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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In: ACS Photonics. - Washington, DC : American Chemical Society (ACS). - 2330-4022. ; 10:6, s. 1748-1755
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Journal article (peer-reviewed)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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| 4. |
- Jeddi, Hossein, et al.
(author)
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Gain and bandwidth of InP nanowire array photodetectors with embedded photogated InAsP quantum discs
- 2021
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In: Nanoscale. - Cambridge : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 13:12, s. 6227-6233
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Journal article (peer-reviewed)abstract
- Here we report on the experimental results and advanced self-consistent real device simulations revealing a fundamental insight into the non-linear optical response of n+-i-n+ InP nanowire array photoconductors to selective 980 nm excitation of 20 axially embedded InAsP quantum discs in each nanowire. The optical characteristics are interpreted in terms of a photogating mechanism that results from an electrostatic feedback from trapped charge on the electronic band structure of the nanowires, similar to the gate action in a field-effect transistor. From detailed analyses of the complex charge carrier dynamics in dark and under illumination was concluded that electrons are trapped in two acceptor states, located at 140 and 190 meV below the conduction band edge, at the interface between the nanowires and a radial insulating SiOx cap layer. The non-linear optical response was investigated at length by photocurrent measurements recorded over a wide power range. From these measurements were extracted responsivities of 250 A W-1 (gain 320)@20 nW and 0.20 A W-1 (gain 0.2)@20 mW with a detector bias of 3.5 V, in excellent agreement with the proposed two-trap model. Finally, a small signal optical AC analysis was made both experimentally and theoretically to investigate the influence of the interface traps on the detector bandwidth. While the traps limit the cut-off frequency to around 10 kHz, the maximum operating frequency of the detectors stretches into the MHz region.
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| 5. |
- Karimi, Mohammad, 1988-, et al.
(author)
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High Responsivity of InP/InAsP Nanowire Array Broadband Photodetectors Enhanced by Optical Gating
- 2019
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In: Nano Letters. - Washington, DC : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 19:12, s. 8424-8430
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Journal article (peer-reviewed)abstract
- High-performance photodetectors operating in the near-infrared (0.75−1.4 μm) and short-wave infrared (1.4−3.0 μm) portion ofthe electromagnetic spectrum are key components in many optical systems.Here, we report on a combined experimental and theoretical study of squaremillimeter array infrared photodetectors comprising 3 million n+−i−n+ In Pnanowires grown by MOVPE from periodically ordered Au seed particles. Thenominal i-segment, comprising 20 InAs0.40P0.60 quantum discs, was grown byuse of an optimized Zn doping to compensate the nonintentional n-doping.The photodetectors exhibit bias- and power-dependent responsivities reachingrecord-high values of 250 A/W at 980 nm/20 nW and 990 A/W at 532 nm/60nW, both at 3.5 V bias. Moreover, due to the embedded quantum discs, thephotoresponse covers a broad spectral range from about 0.70 to 2.5 eV, ineffect outperforming conventional single InGaAs detectors and dual Si/Gedetectors. The high responsivity, and related gain, results from a novel proposed photogating mechanism, induced by the complex charge carrier dynamics involving optical excitation and recombination in the quantum discs and interface traps, which reduces the electron transport barrier between the highly doped n+ contact and the i-segment. The experimental results obtained are in perfect agreement with the proposed theoretical model and represent a significant step forward toward understanding gain in nanoscale photodetectors and realization of commercially viable broadband photon detectors with ultrahigh gain. © 2019 American Chemical Society.
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| 6. |
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| 7. |
- Wallentin, Jesper, et al.
(author)
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InP Nanowire Array Solar Cells Achieving 13.8% Efficiency by Exceeding the Ray Optics Limit.
- 2013
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In: Science. - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 339:6123, s. 1057-1060
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Journal article (peer-reviewed)abstract
- Photovoltaics based on nanowire arrays could reduce cost and materials consumption compared to planar devices, but have exhibited low efficiency of light absorption and carrier collection. We fabricated a variety of millimeter-sized arrays of p-i-n doped InP nanowires and found that the nanowire diameter and the length of the top n-segment were critical for cell performance. Efficiencies up to 13.8% (comparable to the record planar InP cell) were achieved using resonant light trapping in 180-nanometer-diameter nanowires that only covered 12% of the surface. The share of sunlight converted into photocurrent (71%) was six times the limit in a simple ray optics description. Furthermore, the highest open circuit voltage of 0.906 volt exceeds that of its planar counterpart, despite about 30 times higher surface-to-volume ratio of the nanowire cell.
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