- 标题
- 摘要
- 关键词
- 实验方案
- 产品
过滤筛选
- 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
-
Vertical Current Transport in AlGaN/GaN HEMTs on Silicon: Experimental Investigation and Analytical Model
摘要： We investigate the vertical leakage mechanism in metal–organic chemical vapor deposition-grown carbon (C)-doped AlGaN/GaN High Electron Mobility Transistors (HEMTs) on 6-in silicon wafer. Substrate bias polarity-dependentI–Vs, temperature-dependent ?tting, and band diagram analysis pointed to the Poole–Frenkel (P–F) type of conduction mechanism for vertical transport in the devices with breakdown as high as 580 V for a buffer of 4 μm. Trap activation energy of 0.61 eV was estimated from the P–F ?tting which matches well with values reported in the literature. We propose that higher dislocation density leads to shallower traps in the buffer and build an analytical model of dislocation-mediated vertical leakage around this. The variation in leakage as a function of dislocation density at a given ?eld is predicted and is found to be the most abrupt in the range from ～107 to ～109 cm?2 of dislocation density. This can be attributed to a sharp decrease in trap activation energy in the above range of dislocation density, possibly due to complex formation between point defects and dislocations.
关键词： high-electron mobility transistor (HEMT),vertical leakage,Poole–Frenkel (P–F),2-D electron gas,hopping conduction,AlGaN
更新于2025-09-09 09:28:46
-
Relative Roles of Luminance and Fixation in Inducing Dissociated Vertical Divergence
摘要： PURPOSE. We evaluated the roles of luminance and fixation in the pathophysiology of dissociated vertical divergence (DVD). METHODS. Vertical eye position was measured in 6 subjects with DVD (ages 11–47 years, 5 females) and 6 controls (ages 16–40 years, 5 females) using video-oculography (VOG) under conditions of change in fixation and luminance. RESULTS. Subjects with DVD showed the following VOG responses. When fixation was precluded with a translucent filter and bright light was shone into one eye to produce a marked binocular luminance disparity, we found some subjects had a small induced vertical divergence causing the illuminated eye to be lower than the nonilluminated eye (mean (cid:2)1.68 6 1.58, P ? 0.06 compared to no vertical divergence using the signed rank test). When fixation was precluded with a translucent filter, while alternate occlusion produced a mild binocular luminance disparity, we found a smaller vertical divergence of the eyes that was not statistically significant (1.28 6 2.18, P ? 0.3). When alternate occlusion produced reversal of monocular fixation in the dark (with essentially no change in peripheral luminance disparity), there was a significant vertical divergence movement causing the covered eye to be relatively higher than the uncovered eye (7.28 6 3.18, P ? 0.03). The amplitude of this vertical divergence was similar to that measured under conditions of alternate occlusion in a lighted room (where there also was a significant average relative upward movement of the covered eye of 8.18 6 2.98, P ? 0.03). Control subjects showed no vertical divergence under any testing conditions. CONCLUSIONS. Dissociated vertical divergence is mediated primarily by changes in fixation and only to a minor degree by binocular luminance disparity.
关键词： strabismus,videooculography,dissociated vertical divergence,DVD
更新于2025-09-04 15:30:14
-
Sulfur dioxide (SO<sub>2</sub>) vertical column density measurements by Pandora spectrometer over the Canadian oil sands
摘要： Vertical column densities (VCDs) of SO2 retrieved by a Pandora spectral sun photometer at Fort McKay, Alberta, Canada, from 2013 to 2015 were analysed. The Fort McKay site is located in the Canadian oil sands region, approximately 20 km north of two major SO2 sources (upgraders), with total emission of about 45 kt yr?1. Elevated SO2 VCD values were frequently recorded by the instrument, with the highest values of about 9 Dobson Units (DU; DU = 2.69 × 1016 molecules cm?2). Comparisons with co-located in situ measurements demonstrated that there was a very good correlation between VCDs and surface concentrations in some cases, while in other cases, elevated VCDs did not correspond to high surface concentrations, suggesting the plume was above the ground. Elevated VCDs and surface concentrations were observed when the wind direction was from south to southeast, i.e. from the direction of the two local SO2 sources. The precision of the SO2 measurements, estimated from parallel measurements by two Pandora instruments at Toronto, is 0.17 DU. The total uncertainty of Pandora SO2 VCD, estimated using measurements when the wind direction was away from the sources, is less than 0.26 DU (1σ ). Comparisons with integrated SO2 pro?les from concurrent aircraft measurements support these estimates.
关键词： Pandora spectrometer,vertical column density,Sulfur dioxide,oil sands,air quality
更新于2025-09-04 15:30:14
-
Ultimate limit in size and performance of WSe2 vertical diodes
摘要： Precise doping-profile engineering in van der Waals heterostructures is a key element to promote optimal device performance in various electrical and optical applications with two-dimensional layered materials. Here, we report tungsten diselenide- (WSe2) based pure vertical diodes with atomically defined p-, i- and n-channel regions. Externally modulated p- and n-doped layers are respectively formed on the bottom and the top facets of WSe2 single crystals by direct evaporations of high and low work-function metals platinum and gadolinium, thus forming atomically sharp p–i–n heterojunctions in the homogeneous WSe2 layers. As the number of layers increases, charge transport through the vertical WSe2 p–i–n heterojunctions is characterized by a series of quantum tunneling events; direct tunneling, Fowler–Nordheim tunneling, and Schottky emission tunneling. With optimally selected WSe2 thickness, our vertical heterojunctions show superb diode characteristics of an unprecedentedly high current density and low turn-on voltages while maintaining good current rectification.
关键词： current rectification,WSe2,van der Waals heterostructures,quantum tunneling,vertical diodes
更新于2025-09-04 15:30:14
-
Fabrication of vertical alignment liquid crystal cell without forming a conventional polyimide-alignment layer
摘要： A novel preparation method of the vertical alignment polymer film (VAPF) was proposed by polymerisation of the monomers, 2,3-difluoro-4?-[2-(diacryloyl-oxy-hexyl)methyl ester-hexadecyl-oxy]-biphenyl (DFDAMHB) and 2,7-dimethacryloyl-oxy-phenanthrene (DMAPhen), being dissolved in the liquid crystal (LC) material. For obtaining the vertical alignment (VA), the ultraviolet exposure was carried out to the LC cell below the nematic to isotropic transition temperature of the LC material. The VA mode LC cell with the VAPF produced from the monomers DFDAMHB and DMAPhen exhibited enough level of electro-optical and response properties, high voltage holding ratio and low residual direct current voltage.
关键词： vertical alignment polymer film,Liquid crystals,nematic to isotropic transition temperature,monomers,polymerisation
更新于2025-09-04 15:30:14
-
GaN Power Devices – Current Status and Future Directions
摘要： Power conversion losses are pervasive in all areas of electricity consumption, including motion control, lighting, air conditioning, and computation technology. To minimize losses, high efficiency switches are required for the fundamental power conversion units (motors, inverters, and generators) that drive the components. The workhorse of this industry has been silicon-based power switches, but that technology has matured to the fundamental material limits. As a wide bandgap semiconductor, the GaN materials system represents a critical technology for next-generation electronics in many applications due to the high breakdown field, high mobility, and chemical and thermal stability. Devices based on GaN are already well-known to many of us and are used in our daily lives, primarily as the core technology behind solid state lighting based on the GaN light emitting diode (LED), for which Nakamura, Amano, and Akasaki won the Nobel Prize in 2014. In addition GaN-based high electron mobility transistors (HEMTs) have been widely commercialized as RF power amplifiers for communications and radar applications. However, GaN-based devices are relatively nascent in the power conversion field, as most device technology has been dominated by Si and, recently, SiC. Power devices have unique requirements, such as normally-off behavior for fail-safe operation and high field management for high voltage operation, that have proven notoriously difficult in this system, thus an extension of HEMT designs and processing knowledge is not possible.
关键词： power devices,GaN,vertical GaN devices,power conversion,HEMTs
更新于2025-09-04 15:30:14
-
[IEEE 2018 IEEE Symposium on VLSI Technology - Honolulu, HI (2018.6.18-2018.6.22)] 2018 IEEE Symposium on VLSI Technology - Record 47 mV/dec top-down vertical nanowire InGaAs/GaAsSb tunnel FETs
摘要： Pocketed vertical nanowire InGaAs/GaAsSb tunnel FETs (TFET) with sub-threshold swing (SS) reaching 47 mV/dec are demonstrated. The achieved sub-threshold performance is the steepest reported so far for a top-down TFET in the III-V material system. Smooth vertical wires with diameters as narrow as 30 nm are achieved using a CH4 based dry etch process. Drive current at 0.35 V supply voltage approaches 0.7 μA/μm for a fixed Ioff of 1 nA/μm.
关键词： tunnel FETs,InGaAs/GaAsSb,vertical nanowire,sub-threshold swing,III-V material system
更新于2025-09-04 15:30:14
-
Polarimetric remote sensing in oxygen A and B bands: sensitivity study and information content analysis for vertical profile of aerosols
摘要： Theoretical analysis is conducted to reveal the information content of aerosol vertical profile in space-borne measurements of the backscattered radiance and degree of linear polarization (DOLP) in oxygen (O2) A and B bands. Assuming a quasi-Gaussian shape for aerosol vertical profile characterized by peak height H and half width γ (at half maximum), the Unified Linearized Vector Radiative Transfer Model (UNL-VRTM) is used to simulate the Stokes four-vector elements of upwelling radiation at the top of atmosphere (TOA) and their Jacobians with respect to H and γ. Calculations for different aerosol types and different combinations of H and γ values show that the wide range of gas absorption optical depth in O2 A and B band enables the sensitivity of backscattered DOLP and radiance at TOA to the aerosol layer at different altitudes. Quantitatively, DOLP in O2 A and B bands is found to be more sensitive to H and γ than radiance, especially over the bright surfaces (with large visible reflectance). In many O2 absorption wavelengths, the degree of freedom of signal (DFS) for retrieving H (or γ) generally increases with H (and γ) and can be close to unity in many cases, assuming that the composite uncertainty from surface and aerosol scattering properties as well as measurements is less than 5 %. Further analysis demonstrates that DFS needed for simultaneous retrieval of H and γ can be obtained from a combined use of DOLP measurements at ～ 10–100 O2 A and B absorption wavelengths (or channels), depending on the specific values of H. The higher the aerosol layer, the fewer number of channels for DOLP measurements in O2 A and B bands are needed for characterizing H and γ. Future hyperspectral measurements of DOLP in O2 A and B bands are needed to continue studying their potential and their combination with radiance and DOLP in atmospheric window channels for retrieving the vertical profiles of aerosols, especially highly scattering aerosols, over land.
关键词： oxygen A and B bands,radiative transfer model,aerosol vertical profile,polarimetric remote sensing,degree of linear polarization
更新于2025-09-04 15:30:14
-
Smithsonian Astrophysical Observatory Ozone Mapping and Profiler Suite (SAO OMPS) formaldehyde retrieval
摘要： This paper presents our new formaldehyde (H2CO) retrievals, obtained from spectra recorded by the nadir instrument of the Ozone Mapping and Profiler Suite (OMPS) flown on board NASA’s Suomi National Polar-orbiting Partnership (SUOMI-NPP) satellite. Our algorithm is similar to the one currently in place for the production of NASA’s Ozone Monitoring Instrument (OMI) operational H2CO product. We are now able to produce a set of long-term data from two different instruments that share a similar concept and a similar retrieval approach. The ongoing overlap period between OMI and OMPS offers a perfect opportunity to study the consistency between both data sets. The different spatial and spectral resolution of the instruments is a source of discrepancy in the retrievals despite the similarity of the physic assumptions of the algorithm. We have concluded that the reduced spectral resolution of OMPS in comparison with OMI is not a significant obstacle in obtaining good-quality retrievals. Indeed, the improved signal-to-noise ratio of OMPS with respect to OMI helps to reduce the noise of the retrievals performed using OMPS spectra. However, the size of OMPS spatial pixels imposes a limitation in the capability to distinguish particular features of H2CO that are discernible with OMI. With root mean square (RMS) residuals ～ 5×10?4 for individual pixels we estimate the detection limit to be about 7.5 × 1015 molecules cm?2. Total vertical column density (VCD) errors for individual pixels range between 40 % for pixels with high concentrations to 100 % or more for pixels with concentrations at or below the detection limit. We compare different OMI products (SAO OMI v3.0.2 and BIRA OMI v14) with our OMPS product using 1 year of data, between September 2012 and September 2013. The seasonality of the retrieved slant columns is captured similarly by all products but there are discrepancies in the values of the VCDs. The mean biases among the two OMI products and our OMPS product are 23 % between OMI SAO and OMPS SAO and 28 % between OMI BIRA and OMPS SAO for eight selected regions.
关键词： formaldehyde,OMPS,H2CO,retrieval,AMFs,vertical column density,air mass factors,spectral fitting,OMI,VCD
更新于2025-09-04 15:30:14
-
Proposal and Realization of Vertical GaN Nanowire Static Induction Transistor
摘要： Vertical Gallium Nitride (GaN) nanowire Static Induction Transistors (SITs) are proposed and realized for micro display for the first time. A top-down dry etch was employed to form the GaN nanowires with height of ~1.5 μm and diameter of ~350 nm, followed by the SIT fabrication with the gate-all-around design which benefits are better gate control, combined with reduced surface area consumption for improved scaling and integration. Relatively low voltages are required for controlling the vertical current from source to drain. The Ion to Ioff ratio is measured as 2 × 106, which is ~900 times larger than the previous reported GaN fin SIT. These results demonstrated that vertical nanowire SITs by the use of undoped GaN which is typically the template layer for light-emitting diodes (LEDs) will enable voltage-controlled components for new integration schemes and opportunities in micro display technology.
关键词： Vertical Devices,Nanowires,Static Induction Transistor,Schottky gate,GaN
更新于2025-09-04 15:30:14