| 1. |
- Aad, G, et al.
(författare)
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- 2015
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swepub:Mat__t
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| 2. |
- Akram, Muhammad Nadeem, et al.
(författare)
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Influence of base-region thickness on the performance of Pnp transistor-VCSEL
- 2014
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Ingår i: Optics Express. - 1094-4087. ; 22:22, s. 27398-27414
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Tidskriftsartikel (refereegranskat)abstract
- We have recently reported a 980nm GaAs-based three terminal Pnp transistor-vertical-cavity surface-emitting laser (TVCSEL) operating at room temperature with optical power up to 1.8mW. However, the current gain beta = Delta I-c/Delta I-b was near zero just before lasing and became negative after the lasing threshold. The main cause of the negative current gain was found to be a gradual and position-dependent forward-biasing (saturation) of the base-collector junction with increasing bias even before lasing threshold. In this article, detailed multi-physics device simulations are performed to better understand the device physics, and find ways to avoid the premature saturation of the base-collector junction. We have optimized the thickness of the base region as well as its doping concentration and the location of the quantum wells to ensure that the T-VCSEL is in the active mode throughout its range of operation. That is, the emitter-base junction is forward biased and base-collector junction is reversed biased for sweeping the excess charges out of the base region.
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| 3. |
- Asadollahi, Ali, et al.
(författare)
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Fabrication of relaxed germanium on insulator via room temperature wafer bonding
- 2014
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Ingår i: ECS Transactions. - : Electrochemical Society. - 1938-6737. ; , s. 533-541
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Konferensbidrag (refereegranskat)abstract
- We report on the fabrication of, high quality, monocrystalline relaxed Germanium with ultra-low roughness on insulator (GeOI) using low-temperature direct wafer bonding. We observe that a two-step epitaxially grown germanium film fabricated on silicon by reduced pressure chemical vapor deposition can be directly bonded to a SiO2 layer using a thin Al2O3 as bonding mediator. After removing the donor substrate silicon the germanium layer exhibits a complete relaxation without degradation in crystalline quality and no stress in the film. . The results suggest that the fabricated high quality GeOI substrate is a suitable platform for high performance device applications.
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| 4. |
- Asadollahi, Ali, et al.
(författare)
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Fabrication of strained Ge on insulator via room temperature wafer bonding
- 2014
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Ingår i: 2014 15th International Conference on Ultimate Integration on Silicon, ULIS 2014. - : IEEE Computer Society. - 9781479937189 ; , s. 81-84
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Konferensbidrag (refereegranskat)abstract
- This work describes a strained germanium on insulator (GeOI) fabrication process using wafer bonding and etch-back techniques. The strained Ge layer is fabricated epitaxially using reduced pressure chemical vapor deposition (RPCVD). The strained Ge is grown pseudomorphic on top of a partially relaxed Si 0.66Ge0.34 layer. Wafer bonding is performed at room temperature without post-anneal processes and the etch-back steps are performed without mechanical grinding and chemical mechanical polishing (CMP).
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| 5. |
- Durr, Hermann A., et al.
(författare)
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A Closer Look Into Magnetism : Opportunities With Synchrotron Radiation
- 2009
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Ingår i: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 45:1, s. 15-57
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Forskningsöversikt (refereegranskat)abstract
- The unique properties of synchrotron radiation, such as broad energy spectrum, variable light polarization, and flexible time structure, have made it an enormously powerful tool in the study of magnetic phenomena and materials. The refinement of experimental techniques has led to many new research opportunities, keeping up with the challenges put up by modern magnetism research. In this contribution, we review some of the recent developments in the application of synchrotron radiation and particularly soft X-rays to current problems in magnetism, and we discuss future perspectives.
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| 6. |
- Franke, James A, et al.
(författare)
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Agricultural breadbaskets shift poleward given adaptive farmer behavior under climate change
- 2022
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 28:1, s. 167-181
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Tidskriftsartikel (refereegranskat)abstract
- Modern food production is spatially concentrated in global "breadbaskets". A major unresolved question is whether these peak production regions will shift poleward as the climate warms, allowing some recovery of potential climaterelated losses. While agricultural impacts studies to date have focused on currently cultivated land, the Global Gridded Crop Model Intercomparison Project (GGCMI) Phase 2 experiment allows us to assess changes in both yields and the location of peak productivity regions under warming. We examine crop responses under projected end-of-century warming using 7 process-based models simulating 5 major crops (maize, rice, soybeans, and spring and winter wheat) with a variety of adaptation strategies. We find that in no-adaptation cases, when planting date and cultivar choices are held fixed, regions of peak production remain stationary and yield losses can be severe, since growing seasons contract strongly with warming. When adaptations in management practices are allowed (cultivars that retain growing season length under warming and modified planting dates), peak productivity zones shift poleward and yield losses are largely recovered. While most growing-zone shifts are ultimately limited by geography, breadbaskets studied here move poleward over 600 km on average by end of the century under RCP8.5. These results suggest that agricultural impacts assessments can be strongly biased if restricted in spatial area or in the scope of adaptive behavior considered. Accurate evaluation of food security under climate change requires global modeling and careful treatment of adaptation strategies.
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| 7. |
- Franke, James A., et al.
(författare)
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The GGCMI Phase 2 emulators : Global gridded crop model responses to changes in CO2, temperature, water, and nitrogen (version 1.0)
- 2020
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Ingår i: Geoscientific Model Development. - : Copernicus GmbH. - 1991-959X .- 1991-9603. ; 13:9, s. 3995-4018
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Tidskriftsartikel (refereegranskat)abstract
- Statistical emulation allows combining advantageous features of statistical and process-based crop models for understanding the effects of future climate changes on crop yields. We describe here the development of emulators for nine process-based crop models and five crops using output from the Global Gridded Model Intercomparison Project (GGCMI) Phase 2. The GGCMI Phase 2 experiment is designed with the explicit goal of producing a structured training dataset for emulator development that samples across four dimensions relevant to crop yields: Atmospheric carbon dioxide (CO2) concentrations, temperature, water supply, and nitrogen inputs (CTWN). Simulations are run under two different adaptation assumptions: That growing seasons shorten in warmer climates, and that cultivar choice allows growing seasons to remain fixed. The dataset allows emulating the climatological-mean yield response of all models with a simple polynomial in mean growing-season values. Climatological-mean yields are a central metric in climate change impact analysis; we show here that they can be captured without relying on interannual variations. In general, emulation errors are negligible relative to differences across crop models or even across climate model scenarios; errors become significant only in some marginal lands where crops are not currently grown. We demonstrate that the resulting GGCMI emulators can reproduce yields under realistic future climate simulations, even though the GGCMI Phase 2 dataset is constructed with uniform CTWN offsets, suggesting that the effects of changes in temperature and precipitation distributions are small relative to those of changing means. The resulting emulators therefore capture relevant crop model responses in a lightweight, computationally tractable form, providing a tool that can facilitate model comparison, diagnosis of interacting factors affecting yields, and integrated assessment of climate impacts.
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| 8. |
- Franke, James A., et al.
(författare)
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The GGCMI Phase 2 experiment : Global gridded crop model simulations under uniform changes in CO2, temperature, water, and nitrogen levels (protocol version 1.0)
- 2020
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Ingår i: Geoscientific Model Development. - : Copernicus GmbH. - 1991-959X .- 1991-9603. ; 13:5, s. 2315-2336
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Tidskriftsartikel (refereegranskat)abstract
- Concerns about food security under climate change motivate efforts to better understand future changes in crop yields. Process-based crop models, which represent plant physiological and soil processes, are necessary tools for this purpose since they allow representing future climate and management conditions not sampled in the historical record and new locations to which cultivation may shift. However, process-based crop models differ in many critical details, and their responses to different interacting factors remain only poorly understood. The Global Gridded Crop Model Intercomparison (GGCMI) Phase 2 experiment, an activity of the Agricultural Model Intercomparison and Improvement Project (AgMIP), is designed to provide a systematic parameter sweep focused on climate change factors and their interaction with overall soil fertility, to allow both evaluating model behavior and emulating model responses in impact assessment tools. In this paper we describe the GGCMI Phase 2 experimental protocol and its simulation data archive. A total of 12 crop models simulate five crops with systematic uniform perturbations of historical climate, varying CO2, temperature, water supply, and applied nitrogen ("CTWN") for rainfed and irrigated agriculture, and a second set of simulations represents a type of adaptation by allowing the adjustment of growing season length. We present some crop yield results to illustrate general characteristics of the simulations and potential uses of the GGCMI Phase 2 archive. For example, in cases without adaptation, modeled yields show robust decreases to warmer temperatures in almost all regions, with a nonlinear dependence that means yields in warmer baseline locations have greater temperature sensitivity. Inter-model uncertainty is qualitatively similar across all the four input dimensions but is largest in high-latitude regions where crops may be grown in the future.
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| 9. |
- Gustafsson, Oscar, et al.
(författare)
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A performance assessment of type-II interband In0.5Ga 0.5Sb QD photodetectors
- 2013
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Ingår i: Infrared physics & technology. - : Elsevier BV. - 1350-4495 .- 1879-0275. ; 61, s. 319-324
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Tidskriftsartikel (refereegranskat)abstract
- Self-assembled quantum-dot (QD) structures with type-II band alignment to the surrounding matrix material have been proposed as a III/V material approach to realize small-bandgap device structures suitable for photon detection and imaging in the long-wavelength infrared (LWIR) band. Here, we analyze the photoresponse of In0.5Ga0.5Sb/InAs QD photodiodes and estimate the system performance of type-II QD -based photodetectors. A review of alternative design approaches is presented and the choice of matrix material is discussed in terms of band alignment and its effect on the photoresponse. Photodiodes were fabricated consisting of 10 layers of In0.5Ga 0.5Sb QDs grown on InAs (0 0 1) substrates with metal-organic vapor-phase epitaxy (MOVPE). The photoresponse and dark current were measured in single pixel devices as a function of temperature in the range 20-230 K. The quantum efficiency shows an Arrhenius type behavior, which is attributed to hole trapping. This severely limits the detector performance at typical LWIR sensor operating temperatures (60-120 K). A device design with the matrix material InAs0.6Sb0.4 is proposed as a mean to improve the performance by reducing the barrier for hole transport. This can potentially allow type-II InGaSb QDs to be a competitive sensor material for LWIR detection.
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| 10. |
- Hammar, Mattias, et al.
(författare)
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Room-temperature operation of 980-nm transistor-vertical-cavity surface-emitting lasers
- 2013
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Ingår i: 2013 IEEE 6th International Conference on Advanced Infocomm Technology, ICAIT 2013. - : IEEE. - 9781479904655 ; , s. 141-142
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Konferensbidrag (refereegranskat)abstract
- We report on the design, fabrication and characterization of pnp-type 980-nm transistor-vertical-cavity surface-emitting lasers (T-VCSELs). Using an epitaxial regrowth process and a triple-intracavity current injection scheme we demonstrate static performance levels quite comparable to those of conventional VCSELs, including sub-mA threshold base current, mW-range output power and continuous-wave operation at least up to 50°C.
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| 11. |
- Hjörvarsson, Björgvin, et al.
(författare)
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The influence of weak links on magnetic ordering in layered structures
- 2008
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Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 61:1, s. 17008-
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Tidskriftsartikel (refereegranskat)abstract
- We discuss the magnetic ordering in layered magnets with two different inherent ordering temperatures. A [V(12 ML)Fe(2 ML)/V(12 ML)(/Fe(3 ML)](70) superlattice with anti-ferromagnetic interlayer exchange coupling is used for this purpose. The more rapid decrease of the magnetic moment in the 2 monolayer thick Fe layers influences the ordering in a non-trivial way. A distribution of the effective ordering temperature is inferred, originating from a more rapid decrease of the magnetic moment in the near-surface region, as compared to the interior of the sample. The results clearly demonstrate the need to consider all energy and length scales when addressing ordering in materials with finite extension.
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| 12. |
- Minoli, Sara, et al.
(författare)
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Global Response Patterns of Major Rainfed Crops to Adaptation by Maintaining Current Growing Periods and Irrigation
- 2019
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Ingår i: Earth's Future. - 2328-4277. ; 7:12, s. 1464-1480
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Tidskriftsartikel (refereegranskat)abstract
- Increasing temperature trends are expected to impact yields of major field crops by affecting various plant processes, such as phenology, growth, and evapotranspiration. However, future projections typically do not consider the effects of agronomic adaptation in farming practices. We use an ensemble of seven Global Gridded Crop Models to quantify the impacts and adaptation potential of field crops under increasing temperature up to 6 K, accounting for model uncertainty. We find that without adaptation, the dominant effect of temperature increase is to shorten the growing period and to reduce grain yields and production. We then test the potential of two agronomic measures to combat warming-induced yield reduction: (i) use of cultivars with adjusted phenology to regain the reference growing period duration and (ii) conversion of rainfed systems to irrigated ones in order to alleviate the negative temperature effects that are mediated by crop evapotranspiration. We find that cultivar adaptation can fully compensate global production losses up to 2 K of temperature increase, with larger potentials in continental and temperate regions. Irrigation could also compensate production losses, but its potential is highest in arid regions, where irrigation expansion would be constrained by water scarcity. Moreover, we discuss that irrigation is not a true adaptation measure but rather an intensification strategy, as it equally increases production under any temperature level. In the tropics, even when introducing both adapted cultivars and irrigation, crop production declines already at moderate warming, making adaptation particularly challenging in these areas.
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| 13. |
- Müller, Christoph, et al.
(författare)
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Exploring uncertainties in global crop yield projections in a large ensemble of crop models and CMIP5 and CMIP6 climate scenarios
- 2021
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9318 .- 1748-9326. ; 16:3
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Tidskriftsartikel (refereegranskat)abstract
- Concerns over climate change are motivated in large part because of their impact on human society. Assessing the effect of that uncertainty on specific potential impacts is demanding, since it requires a systematic survey over both climate and impacts models. We provide a comprehensive evaluation of uncertainty in projected crop yields for maize, spring and winter wheat, rice, and soybean, using a suite of nine crop models and up to 45 CMIP5 and 34 CMIP6 climate projections for three different forcing scenarios. To make this task computationally tractable, we use a new set of statistical crop model emulators. We find that climate and crop models contribute about equally to overall uncertainty. While the ranges of yield uncertainties under CMIP5 and CMIP6 projections are similar, median impact in aggregate total caloric production is typically more negative for the CMIP6 projections (+1% to −19%) than for CMIP5 (+5% to −13%). In the first half of the 21st century and for individual crops is the spread across crop models typically wider than that across climate models, but we find distinct differences between crops: globally, wheat and maize uncertainties are dominated by the crop models, but soybean and rice are more sensitive to the climate projections. Climate models with very similar global mean warming can lead to very different aggregate impacts so that climate model uncertainties remain a significant contributor to agricultural impacts uncertainty. These results show the utility of large-ensemble methods that allow comprehensively evaluating factors affecting crop yields or other impacts under climate change. The crop model ensemble used here is unbalanced and pulls the assumption that all projections are equally plausible into question. Better methods for consistent model testing, also at the level of individual processes, will have to be developed and applied by the crop modeling community.
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| 14. |
- Müller, Christoph, et al.
(författare)
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Substantial Differences in Crop Yield Sensitivities Between Models Call for Functionality-Based Model Evaluation
- 2024
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Ingår i: Earth's Future. - 2328-4277. ; 12:3
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Tidskriftsartikel (refereegranskat)abstract
- Crop models are often used to project future crop yield under climate and global change and typically show a broad range of outcomes. To understand differences in modeled responses, we analyzed modeled crop yield response types using impact response surfaces along four drivers of crop yield: carbon dioxide (C), temperature (T), water (W), and nitrogen (N). Crop yield response types help to understand differences in simulated responses per driver and their combinations rather than aggregated changes in yields as the result of simultaneous changes in various drivers. We find that models' sensitivities to the individual drivers are substantially different and often more different across models than across regions. There is some agreement across models with respect to the spatial patterns of response types but strong differences in the distribution of response types across models and their configurations suggests that models need to undergo further scrutiny. We suggest establishing standards in model evaluation based on emergent functionality not only against historical yield observations but also against dedicated experiments across different drivers to analyze emergent functional patterns of crop models.
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| 15. |
- Reuterskiöld Hedlund, Carl, et al.
(författare)
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Epitaxial growth, fabrication and analysis of vertical-cavity surface-emitting transistor lasers
- 2015
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The vertical-cavity surface-emitting transistor-laser (T-VCSEL) represents a new device paradigm with potential capability to meet upcoming requirements on low-cost power-efficient emitters for data rates up to 100 Gbit/s. However, the performance optimization of such devices requires precise control of carrier dynamics and optical losses that impose significant challenges on the epitaxial growth and fabrication processes. Here, we review the fabrication process of AlGaAs/InGaAs/GaAs pnp-type T-VCSELs based on epitaxial regrowth confinement, modulation doping, triple-intracavity contacting and non-conducting mirrors. The resulting static performance characteristics include threshold current, output power and high-temperature-performance in parity with conventional diode-type VCSELs.
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| 16. |
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| 17. |
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| 18. |
- Xiang, Yu, et al.
(författare)
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AlGaAs/GaAs/InGaAs pnp-type vertical-cavity surface-emitting transistor-lasers
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We report on the design, fabrication and analysis of vertical-cavity surface-emitting transistor-lasers (T-VCSELs) based on the homogeneous integration of an InGaAs/GaAs VCSEL and an AlGaAs/GaAs pnp-heterojunction bipolar transistor (HBT). Epitaxial regrowth confinement, modulation doping, intracavity contacting and non-conducting mirrors are used to ensure a low-loss structure, and a variety of design variations are investigated for a proper internal biasing and current injection to ensure a wide operating range. Optimized devices show mW-range output power, mA-range base threshold current and high-temperature operation to at least 60°C with the transistor in its active mode of operation for base currents well beyond threshold. Current confinement schemes based on pnp-blocking layers or a buried tunnel junction are investigated as well as asymmetric current injection to improve the lateral feeding.
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| 19. |
- Xiang, Yu, et al.
(författare)
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AlGaAs/GaAs/InGaAs pnp-type vertical-cavity surface-emitting transistor-lasers
- 2015
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Ingår i: Optics Express. - 1094-4087. ; 23:12, s. 15680-15699
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Tidskriftsartikel (refereegranskat)abstract
- We report on the design, fabrication and analysis of vertical-cavity surface-emitting transistor-lasers (T-VCSELs) based on the homogeneous integration of an InGaAs/GaAs VCSEL and an AlGaAs/GaAs pnp-heterojunction bipolar transistor (HBT). Epitaxial regrowth confinement, modulation doping, intracavity contacting and non-conducting mirrors are used to ensure a low-loss structure, and a variety of design variations are investigated for a proper internal biasing and current injection to ensure a wide operating range. Optimized devices show mW-range output power, mA-range base threshold current and high-temperature operation to at least 60 degrees C with the transistor in its active mode of operation for base currents well beyond threshold. Current confinement schemes based on pnp-blocking layers or a buried tunnel junction are investigated as well as asymmetric current injection for reduced extrinsic resistances.
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| 20. |
- Xiang, Yu, et al.
(författare)
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Minority current distribution in InGaAs/GaAs transistor-vertical-cavity surface-emitting laser
- 2013
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Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 102:19, s. 191101-
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Tidskriftsartikel (refereegranskat)abstract
- We compare experimental data with three-dimensional numerical calculations of the local minority current in an InGaAs/GaAs transistor vertical-cavity surface-emitting laser at different bias levels. It is demonstrated that lateral potential variations within the device greatly affect the transistor operating conditions. As a result, it locally operates in the active mode in the center of the device, allowing for efficient stimulated recombination, while it globally operates in the saturation regime as reflected by the measured current-voltage characteristics. This allows for excellent laser performance, including mW-range output power, sub-mA threshold base current, and continuous-wave operation well above room temperature.
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| 21. |
- Xiang, Yu, et al.
(författare)
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Performance Optimization of GaAs-Based Vertical-Cavity Surface-Emitting Transistor-Lasers
- 2015
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Ingår i: IEEE Photonics Technology Letters. - : IEEE Press. - 1041-1135 .- 1941-0174. ; 27:7, s. 721-724
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Tidskriftsartikel (refereegranskat)abstract
- We report on the optimization of pnp-type verticalcavity surface-emitting transistor-lasers based on the fusion between an AlGaAs/GaAs heterojunction bipolar transistor and an InGaAs/GaAs VCSEL using an epitaxial regrowth process. It is shown how a proper design of the base region can extend the transistor active range of operation well beyond lasing threshold, thereby resulting in typical transistor laser operational characteristics including mW-range output power, mA-range base threshold current, record-low power dissipation under laser operation, and continuous-wave operation up to at least 60°C. A pronounced breakdown in the collector current characteristics in the limit of high base current and/or emitter-collector voltage accompanied by a quenching of the optical output power is interpreted as being related to quantum well band-filling.
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| 22. |
- Yu, Xingang, et al.
(författare)
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1.3 μm Buried Tunnel junction InGaAs/GaAs VCSELs
- 2013
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Vertical cavity surface emitting lasers (VCSELs) working at 1.3μm are potential cost- and power-efficient sources for medium-range optical networks. However, they are still waiting for their commercial breakthrough due to several technological challenges related to the need for complex materials systems and/or fabrication methods. Nevertheless, many efforts have been devoted to solve the problem, also yielding some excellent results. Alter-native approaches we have previously presented are In-GaAs/GaAs 1.3-μm VCSELs based on oxidation con-finement or with an epitaxial regrowth of a pnp block-ing structure. Here we demonstrate a buried-tunnel junction (BTJ) current confinement scheme to improve the static and dynamic performance.
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| 23. |
- Yu, Xingang, et al.
(författare)
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Room-temperature operation of transistor vertical-cavity surface-emitting laser
- 2013
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Ingår i: Electronics Letters. - : Institution of Engineering and Technology (IET). - 0013-5194 .- 1350-911X. ; 49:3, s. 208-209
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Tidskriftsartikel (refereegranskat)abstract
- The first room-temperature operation of a transistor vertical-cavity surface-emitting laser (T-VCSEL) is demonstrated. Fabricated using an epitaxial regrowth process, the T-VCSEL is electrically a pnp-type bipolar junction transistor and consists of an undoped AlGaAs/GaAs bottom DBR, an InGaAs triple-quantum-well active layer, an Si/SiO2 dielectric top DBR, and an intracavity contacting scheme with three electrical terminals. The output power is controlled by the base current in combination with the emitter-collector voltage, showing a voltage-controlled operation mode. A low threshold base-current of 0.8 mA and an output power of 1.8 mW have been obtained at room temperature. Continuous-wave operation was performed up to 50 degrees C.
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| 24. |
- Zabel, Florian, et al.
(författare)
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Large potential for crop production adaptation depends on available future varieties
- 2021
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 27:16, s. 3870-3882
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Tidskriftsartikel (refereegranskat)abstract
- Climate change affects global agricultural production and threatens food security. Faster phenological development of crops due to climate warming is one of the main drivers for potential future yield reductions. To counter the effect of faster maturity, adapted varieties would require more heat units to regain the previous growing period length. In this study, we investigate the effects of variety adaptation on global caloric production under four different future climate change scenarios for maize, rice, soybean, and wheat. Thereby, we empirically identify areas that could require new varieties and areas where variety adaptation could be achieved by shifting existing varieties into new regions. The study uses an ensemble of seven global gridded crop models and five CMIP6 climate models. We found that 39% (SSP5-8.5) of global cropland could require new crop varieties to avoid yield loss from climate change by the end of the century. At low levels of warming (SSP1-2.6), 85% of currently cultivated land can draw from existing varieties to shift within an agro-ecological zone for adaptation. The assumptions on available varieties for adaptation have major impacts on the effectiveness of variety adaptation, which could more than half in SSP5-8.5. The results highlight that region-specific breeding efforts are required to allow for a successful adaptation to climate change.
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| 25. |
- Zabel, Thomas, et al.
(författare)
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Auger recombination in In(Ga)Sb/InAs quantum dots
- 2015
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Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 106:1
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Tidskriftsartikel (refereegranskat)abstract
- We report on the epitaxial formation of type II In0.5Ga0.5Sb/InAs and InSb/InAs quantum dot ensembles using metal organic vapor phase epitaxy. Employing scanning tunneling spectroscopy, we determine spatial quantum dot dimensions smaller than the de Broglie wavelength of InGaSb, which strongly indicates a three dimensional hole confinement. Photoluminescence spectroscopy at low temperatures yields an enhanced radiative recombination in the mid-infrared regime at energies of 170-200 meV. This luminescence displays a strong excitation power dependence with a blueshift indicating a filling of excited quantum dot hole states. Furthermore, a rate equation model is used to extract the Auger recombination coefficient from the power dependent intensity at 77 K yielding values of 1.35 x 10(-28) cm(6)/s for In0.5Ga0.5Sb/InAs quantum dots and 1.47 x 10(-27) cm(6)/s for InSb/InAs quantum dots, which is about one order of magnitude lower as previously obtained values for InGaSb superlattices.
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