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- 2018
- Dual Material Gate (DMG)
- Vertical TFET
- Single Material Gate(SMG)
- Band-to-band tunneling (BTBT)
- Electronic Science and Technology
- National Institute of Technology Silchar
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - A New Model for P-Band Pol-InSAR Based on Gamma Distribution
摘要： This work proposes a forest model based on Gamma distribution to better describe the forest vertical structure for height inversion using P-band polarimetric synthetic aperture radar interferometry (Pol-InSAR) data. The proposed model takes into account the forest vertical heterogeneity and asymmetry, to which volume interferometric coherence is sensitive. The interferometric coherence associated with a volume where the vertical backscattered power varies following a Gamma distribution is derived. The effect of scattering center height standard deviation and mean elevation to the volume interferometric coherence is investigated. Finally, the strategy of multi-baseline on the proposed model for forest height inversion using P-band Pol-InSAR data is proposed.
关键词： P-band Pol-InSAR,forest model,Gamma distribution,vertical heterogeneity
更新于2025-09-23 15:22:29
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Vertical fine structure and time evolution of plasma irregularities in the Es layer observed by a high-resolution Ca+ lidar
摘要： The vertical fine structures and the time evolution of plasma irregularities in the sporadic E (Es) layer were observed via calcium ion (Ca+) density measurements using a resonance scattering lidar with a high time-height resolution (5 s and 15 m) at Tachikawa (35.7°N, 139.4°E) on December 24, 2014. The observation successfully provided clearer fine structures of plasma irregularities, such as quasi-sinusoidal height variation, localized clumps, “cats-eye” structures, and twist structures, in the sporadic Ca+ (Ca+s) layers at around 100 km altitude. These fine structures suggested that the Kelvin–Helmholtz instabilities occurred in the neutral atmosphere whose density changed temporarily or spatially. The maximum Ca+ density in the Ca+s layer was two orders of magnitude smaller than the maximum electron density estimated from the critical frequency (foEs) simultaneously observed by the ionosonde at Kokubunji (35.7°N, 139.5°E). A strong positive correlation with a coefficient of 0.91 suggests that Ca+ contributes forming the Es layer as well as major metallic ions Fe+ and Mg+ in the lower thermosphere. Moreover, the formation of a new Ca+s layer at 110 km and the upward motions of the Ca+s layers at 100 km and 110 km were observed just after the sunrise time at the conjugation point. Although the presence or absence of a causal relationship with the sunrise time was not clear, a possible explanation for the formation and the upward motions of the Ca+s layers was the occurrence of strong horizontal wind, rather than the enhancement of the eastward electric field.
关键词： Calcium ion (Ca+) density,Ion upward flow,Mid-latitude,Resonance scattering lidar,Kelvin–Helmholtz instability,Sporadic E (Es) layer,Vertical fine structure,Lower thermosphere
更新于2025-09-23 15:22:29
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Two-dimensional g-C3N4/TiO2 Nanocomposites as Vertical Z-scheme Heterojunction for Improved Photocatalytic Water Disinfection
摘要： Developing highly active photocatalysts towards effective microorganism inactivation is a green and energy-smart strategy in response to the growing demands to water quality under the background of the water crisis. Here, a vertical face-to-face heterojunction was fabricated by horizontally assembling TiO2 nanosheets with {001} facets exposed on graphitic carbon nitride (g-C3N4) sheets through a facile hydrothermal driving coupling. The vertical heterojunction could almost completely disinfect 103 CFU/mL E. coli within 30 min under solar light, which was more efficient than the physically mixed composite and pure g-C3N4 and TiO2. The two-dimensional (2D) morphology provides ample surface area in forming the vertical heterojunction and enables intimate contact which is advantageous to charge transfer between g-C3N4 and TiO2. A Z-scheme charge transportation mechanism is confirmed through band structure analysis and reactive species (RSs) probing and trapping experiments. In comparison with physically mixed composite and the single-phase counterparts, the nanocomposite based on Z-scheme electron transfer mode effectively prompts charge pair dissociation and subsequently encourages bacterial inactivation by boosting the generation of RSs. The constructing vertical Z-scheme heterojunction highlights the potential of 2D nanomaterials for accelerated water sterilization.
关键词： photocatalysis,Z-scheme heterojunction,vertical heterojunction,two-dimensional materials,water disinfection
更新于2025-09-23 15:21:21
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A detailed comparison of measured and simulated optical properties of a short-period GaAs/Al <sub/><i>x</i> </sub> Ga <sub/> 1a?? <i>x</i> </sub> As distributed Bragg reflector
摘要： A 6-period GaAs/Al0.9Ga0.1As distributed Bragg re?ector (DBR) has been grown and its optical properties have been both measured and simulated. Incremental improvements were made to the simulation, allowing it to account for internal consistency error, incorrect layer thicknesses, and absorption due to substrate doping to improve simulation accuracy. A compositional depth pro?le using secondary-ion mass spectrometry (SIMS) has been taken and shows that the Al fraction averages 88.0% ± 0.3%. It is found that the amplitude of the transmission is signi?cantly affected by absorption in the n-doped GaAs substrate, even though the energy of the transmitted light is well below the GaAs band gap. The wavelength of the features in the transmission spectrum are mostly affected by DBR layer thicknesses. On the other hand, the transmission spectrum is found to be relatively tolerant to changes to Al fraction.
关键词： optical simulation,AlGaAs,distributed Bragg re?ector,SIMS,cross section,telecoms,vertical cavity
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE Research and Applications of Photonics in Defense Conference (RAPID) - Miramar Beach, FL, USA (2019.8.19-2019.8.21)] 2019 IEEE Research and Applications of Photonics in Defense Conference (RAPID) - Small Batch Production and Test of Custom Support Electronics for Infrared LED Scene Projectors
摘要： This letter reports a GaN vertical trench metal–oxide–semiconductor field-effect transistor (MOSFET) with normally-off operation. Selective area regrowth of n+-GaN source layer was performed to avoid plasma etch damage to the p-GaN body contact region. A metal-organic-chemical-vapor-deposition (MOCVD) grown AlN/SiN dielectric stack was employed as the gate “oxide”. This unique process yielded a 0.5-mm2-active-area transistor with threshold voltage of 4.8 V, blocking voltage of 600 V at gate bias of 0 V, and on-resistance of 1.7 Ω at gate bias of 10 V.
关键词： GaN,vertical transistor,MOSFET,power semiconductor devices
更新于2025-09-23 15:21:01
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Controllable orientations for Sb <sub/>2</sub> S <sub/>3</sub> solar cells by vertical VTD method
摘要： Antimony sulfide (Sb2S3) is a promising photoelectric material because of its wide bandgap approximately 1.7 eV for next-generation solar cells, high optical absorption coefficient, and its green and earth-abundant constituents. Different to traditional cubic structure photovoltaic materials, Sb2S3 holds one-dimensional crystal structure and its thin film with [hk1] preferred orientation shows one-order-higher carrier transport mobility. However, all the reported Sb2S3 films exhibited [hk0] preferred orientation on CdS-based superstrate device structure up to now. Thus, it is indispensable to study the controllable-orientations Sb2S3 film deposition and the relationship between the orientation and performances. In this paper, we develop a vertical vapor transport deposition (V-VTD) method, which can tune the preferred orientation of Sb2S3 thin film from [hk0] to [hk1] by reaction recipe monitoring. Combining the experiment results, a reasonable deposition/reevaporation competing model is suggested to explain above orientation conversion mechanism. The device efficiency increases from less than 2% to about 4% with the orientation of Sb2S3 film changing from [hk0] to [hk1]. By fine regulating the technique of deposition, the device with [hk1] orientation has better crystallinity, lower interface recombination, and higher built-in voltage comparing with the [hk0] one. Finally, a champion power conversion efficiency (PCE) of 4.5% has been achieved, and the VOC of 730 mV is the top value among the Sb2S3 solar cells. The present versatile orientation tuning strategy could overcome the bottleneck of strong anisotropic materials and show high potential for noncubic material deposition and related optoelectronic device performance enhancement.
关键词： vertical vapor transport deposition,solar cell,controllable orientations,Sb2S3,orientation conversion mechanism
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE 2nd British and Irish Conference on Optics and Photonics (BICOP) - London, United Kingdom (2019.12.11-2019.12.13)] 2019 IEEE 2nd British and Irish Conference on Optics and Photonics (BICOP) - A Two-Tier Inverse Taper based Vertical Coupler for Photonic Integrated Circuits
摘要： A low-loss, compact, two-tier spot size-converter (SSC) has been designed and demonstrated to couple light between silicon (Si) and silicon nitride (SiNx) platforms. The high index contrast between the materials is accomplished by matching the optical mode impedance of Si and SiNx. This allows the achievement of record low coupling loss of 0.058 ± 0.01 dB per transition at 1525 nm. The geometric parameters of the vertically integrated SSC were optimized to ensure the adiabatic transition of the optical mode from Si-to-SiNx and vice-versa. The SSC converter shows excellent broadband coupling over 100 nm bandwidth at telecom wavelengths.
关键词： spot size converters,two-tier tapers,vertical coupling
更新于2025-09-23 15:21:01
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Polymer-Silica Hybrid On-Chip Amplifier with Vertical Pumping Method
摘要： This article demonstrates a multilayer polymer-silica hybrid on-chip amplifier combining mode division multiplexing method. The multilayer amplifier consists of a pumping silica waveguide and an amplifying polymer waveguide. The pumping waveguide possesses the stability and the high damage threshold. The amplifying waveguide takes the advantages of the high compatibility and the high doping rate. The vertical pump of mode division multiplexing method can introduce the pumping light into the amplifying waveguide at any desired position of the chip. By the isolation method between signal and pumping light, the pumping light can be coupled into the amplifying waveguide, while the signal light cannot be coupled into the pumping waveguide. The parameters of doping rates, waveguide lengths, overlap factors, coupling parameters are calculated to optimize the gain characteristics of the amplifier. The amplifier with three position-optimized pumping light was designed achieving a maximum gain of 33.89 dB/cm with a waveguide length of 6 cm, a signal power of 0.1 mW and a pumping power of 300 mW. This polymer-silica hybrid amplifier is promising for the on-chip loss compensation of the 3D photonic integrated circuits and all optical transistors.
关键词： vertical pumping method,on-chip amplifier,polymer-silica hybrid,mode division multiplexing,3D photonic integrated circuits
更新于2025-09-23 15:21:01
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<i>(Invited) The Scaling-Down and Performance Optimization of InAs Nanowire Field Effect Transistors</i>
摘要： Due to their fascinating properties, InAs nanowires have drawn great attention for the channel material in future transistors. Scaling-down has been an effective way to improve the performance of transistors continuously for decades. Here, we review our recent progresses on InAs nanowire field effect transistors (FETs) when they are scaled down. Our group investigates the electrical characteristics of InAs nanowire thinner than 10 nm. Both the size-effect and the contact properties of ultrathin nanowires are explored. Moreover, the effects of InAs crystal phase and orientation are studied for further optimizing the device performance. In addition, FETs with partial gate are studied to suppress the BTBT-induced off-current. Furthermore, to improve the electrostatics control of the gate, our group develops a method to fabricate vertical GAA FETs with all-metal electrodes based on self-catalyzed grown InAs nanowire arrays.
关键词： orientation,crystal phase,performance optimization,field effect transistors,partial gate,vertical GAA FETs,InAs nanowires,scaling-down
更新于2025-09-23 15:21:01
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Study on the Droplet Transition Models in Laser Welding with Filler Wire
摘要： This study is intended to examine the droplet transition in the welding process. Tests were performed using a high-speed camera to assess the effect of the vertical distance between the laser–wire intersection and workpiece (H) on droplet transition. Meanwhile, forces on the droplet were analyzed to evaluate the transition model during laser welding with filler wire. The results showed transition frequency, that droplet size and forces of the model all changed with H level changing. Droplet transition and the welding process showed stability at an H level of 1 mm. Based on the liquid bridge transition model, the droplet was transferred to the molten pool in the state of balance, while the droplet entered into the molten pool under non-equilibrium state during globular transition.
关键词： Droplet transition,Laser welding with filler wire,Vertical distance between the laser–wire intersection and workpiece,Force analysis of droplet
更新于2025-09-23 15:21:01