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Phonon-assisted tunneling in direct-bandgap semiconductors
摘要： In tunnel ?eld-effect transistors, trap-assisted tunneling (TAT) is one of the probable causes for degraded subthreshold swing. The accurate quantum-mechanical (QM) assessment of TAT currents also requires a QM treatment of phonon-assisted tunneling (PAT) currents. Therefore, we present a multi-band PAT current formalism within the framework of the quantum transmitting boundary method. An envelope function approximation is used to construct the electron-phonon coupling terms corresponding to local Fr?hlich-based phonon-assisted inter-band tunneling in direct-bandgap III-V semiconductors. The PAT current density is studied in up to 100 nm long and 20 nm wide p-n diodes with the 2- and 15-band material description of our formalism. We observe an inef?cient electron-phonon coupling across the tunneling junction. We further demonstrate the dependence of PAT currents on the device length, for our non-self-consistent formalism which neglects changes in the electron distribution function caused by the electron-phonon coupling. Finally, we discuss the differences in doping dependence between direct band-to-band tunneling and PAT current.
关键词： phonon-assisted tunneling,quantum-mechanical modeling,tunnel ?eld-effect transistors,electron-phonon coupling,direct-bandgap semiconductors
更新于2025-09-23 15:22:29
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GaN Integration Technology, an Ideal Candidate for High-Temperature Applications: A Review
摘要： In many leading industrial applications such as aerospace, military, automotive, and deep-well drilling, extreme temperature environment is the fundamental hindrance to the use of microelectronic devices. Developing an advanced technology with robust electrical and material properties dedicated for high-temperature environments represents a significant progress allowing to control and monitor the harsh environment regions. It may avoid using cooling structures while improving the reliability of the whole electronic systems. As a wide bandgap semiconductor, gallium nitride is considered as an ideal candidate for such environments, as well as in high-power and high-frequency applications. We review in this paper the main reasons that offer superiority to GaN devices over better-known technologies such as silicon (Si), silicon-on-insulator, gallium arsenide (GaAs), silicon germanium (SiGe), and silicon carbide (SiC). The theory of operation and main challenges at high temperature are discussed, notably those related to materials and contacts. In addition, the main limitations of GaN, including the technological (thermal and chemical) and intrinsic (current collapse and device self-heating) features are provided. In addition, the GaN devices recently developed for high-temperature applications are examined.
关键词： wide-bandgap semiconductors,high-temperature electronics,Extreme temperature applications,gallium-nitride technology
更新于2025-09-23 15:22:29
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Design and Optimization of a Solar Power Conversion System for Space Applications
摘要： This manuscript details a design method for a 500kW solar power based microgrid system for space applications. The design method utilizes multi-objective optimization with the Genetic Algorithm considering four parameters that characterize solar power based microgrids (battery voltage, PV maximum power, PV maximum power point voltage, and number of panels per string). The final optimization metric is the ratio of daily average deliverable power to total system mass (W/kg) metric. The microgrid system is composed of a number of modular DC-DC micro-converters, of which four topologies (buck, boost, buck-boost and non-inverting buck-boost) are evaluated and compared. The non-inverting buck-boost converter is determined to be the best candidate, and the optimal system characteristics are provided and analyzed. The final system design achieves a specific power of 35.56W/kg, with optimized result of 743.7V battery voltage, 439.5W PV maximum power, 182.7V PV maximum voltage, and three panels per string. Based on the optimizations results, a prototype is designed, tested, and analyzed in terms of efficiency and low temperature reliability. The converter achieved a peak efficiency of 98.4%, a power density of 3.54W/cm3, a specific power of 3.76W/g, and operated for over 267 hours of 11-minute low temperature cycles from 0oC to -140oC.
关键词： low temperature testing,photovoltaic systems,wide band gap semiconductors,maximum power point trackers,design optimization,non-inverting buck-boost,space exploration,system-level design,DC-DC power converters,microgrids
更新于2025-09-23 15:22:29
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Synthesis and Electrical Transport Properties of CuInGaTe2
摘要： Copper Indium Gallium di-telluride (CIGT) single crystals were synthesized by a special modified Bridgman technique for crystal growth. Our XRD patterns clearly exhibited single phase. The temperature dependence of the electrical conductivity σ(T), Hall coefficient RH(T) in CuInGaTe2 single crystals have been demonstrated over the temperature range 143-558 K for the first time. The Hall coefficient sign confirms the samples displays the p-type conducting. The temperature dependence of the conductivity, Hall coefficient, Hall mobility, and charge carriers concentration were investigated were presented with a clear and effective pictures. CuInGaTe2 single crystals revealed electrical band gaps (or "transport gaps") ranging from 0.64 eV to 0.85 eV. The results obtained from electrical conductivity and carrier concentration revealed the sample p-type with acceptor energy level equal to ≈ 0.027 eV. From the obtained experimental data, the main fundamental physical constants and others for crystals under consideration have been estimated.
关键词： Single crystals,Electrical conductivity,Cu–III–VI2 Chalcopyrite semiconductors
更新于2025-09-23 15:22:29
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Photoelectrochemical water splitting with p-type metal oxide semiconductor photocathodes Youn Jeong Jang[a] and Jae Sung Lee*[a]
摘要： Photoelectrochemical (PEC) water splitting is a promising way to produce clean and sustainable hydrogen fuel. Solar hydrogen production using p-type metal oxide semiconductor photocathodes has not been studied as extensively as n-type metal oxide semiconductor photoanodes and p-type PV-grade non-oxide semiconductor photocathodes. Copper-based oxide photocathodes show relatively good conductivity but suffer from instability in an aqueous solution under illumination. On the other hands, Fe-based metal oxide photocathodes demonstrate more stable PEC performance, but have problems in charge separation and transport. In this mini-review article, we provide an overview of the recent progress in p-type metal oxide-based photocathodes for PEC water reduction. Although these materials are not fully developed up to their potential performance, the involved challenges have been identified and strategies to overcome the limitations have been proposed. Future research in this field should address these issues and challenges in addition to discovery of new materials.
关键词： metal oxides,p-type semiconductors,photoelectrochemical cell,photocathodes,solar water splitting
更新于2025-09-23 15:22:29
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Tertiary Amines Differentiated from Primary and Secondary Amines by Active Ester-Functionalized Hexabenzoperylene in Field Effect Transistors
摘要： Herein, we report two novel derivatives of hexabenzoperylene (HBP) that are functionalized with ester groups. Methyl acetate functionalized HBP (1) in single crystals self-assembles into a supramolecular nanosheet, which has a two-dimensional π-stack of HBP sandwiched between two layers of ester groups. With the same self-assembly motif, active ester-functionalized HBP (2) in field effect transistors has enabled differentiation of tertiary amines from primary and secondary amines, in agreement with the fact that active ester reacts with primary and secondary amines but not with tertiary amines to form amides.
关键词： sensors,organic field effect transistors,organic semiconductors,self-assembly,arenes
更新于2025-09-23 15:22:29
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Transport models in disordered organic semiconductors and their application to the simulation of thin-film transistors
摘要： Relevant organic thin-film transistor (OTFT) simulation software must account for the main specificities of organic semiconductors (OSC) in term of free carriers’ density of states, transport mechanisms, and injection/collection properties from/to the device contacts. Among the parameters impacting the OTFT performance the carrier mobility is a key parameter. Usual methods to extract the mobility from current-voltage (I-V) measurements lead to obtained only an apparent, or effective, mobility. The value of the apparent mobility is different of the intrinsic channel organic semiconductor mobility. Despite this effective mobility actually determines most of a given device performance, therefore providing a very useful technology benchmark, it does not describe the intrinsic organic semiconductor material transport properties, and may even be misleading in the route to improve the OTFT fabrication process. To obtain a better understanding of the transport properties in OSCs using OTFT electrical characterization, implementing an appropriate physical mobility model in an OTFT I-V simulation software is a good way. The present paper gives a review of the carrier mobility models which can be implemented in OTFT simulation software. The review is restricted to the analytical and semi-analytical physical models taking into account the temperature, the carrier concentration and the electric field dependence of the carrier mobility in disordered OSCs.
关键词： mobility,transport,modeling,organic semiconductors,Organic thin-film transistor (OTFT)
更新于2025-09-23 15:22:29
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Ferromagnetism and Carrier Transport in n-type Diluted Magnetic Semiconductors Ge0.96?xBixFe0.04Te Thin Film
摘要： The structural, Hall effect, electronic transport, and magnetic properties of Ge0.96?xBixFe0.04Te epitaxial thin film as prepared by pulsed laser deposition technique were reported. X-ray diffraction patterns including linear scans and phi scans confirmed that all films are high quality epitaxy and crystallinity. With the substitution of high valence Bi for Ge element, we found that the previous carriers of hole were changed to electron, which was testified by the negative slopes obtained from the measurements of Hall effect under different temperatures. The electronic transports show a typical semiconductor behavior and can be understood by the small polaron hopping model because the lattice distortions increase the electron-phonon interaction. An obvious ferromagnetic properties occur in the high Bi-doping Ge0.64Bi0.32Fe0.04Te rather than in that with low Bi-doping concentration, indicating that the ferromagnetic establishment is entirely dependent on carrier’s transmissions. The first-principles calculation performed on this system also reveals that the ferromagnetic state exactly exists in the present n-type diluted magnetic semiconductors with Bi co-dopants.
关键词： N-type semiconductor,Ferromagnetism,Diluted magnetic semiconductors
更新于2025-09-23 15:22:29
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Graphene role in improved solar photocatalytic performance of TiO2-RGO nanocomposite
摘要： TiO2-RGO (TG) nanocomposite applied as photocatalysts have been synthesized via a facile low-temperature wet chemistry process, during which the reduction of graphene oxide (RGO) and the growth of titanium dioxide (TiO2) nanoparticles on the RGO nanosheets are achieved simultaneously. RGO role in TG nanocomposites as photocatalysts were analyzed in methylene blue photocatalytic degradation under UV and solar irradiation. The TG nanocomposites were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, Raman spectroscopy and transmission electron microscopy. The photocatalytic efficiency of the TG-30 sample under UV and TG-45 solar irradiation was ～7 and ～5 times that of pristine TiO2, respectively. The enhancement of the photocatalytic activity with UV irradiation in TG was attributed to the high separation efficiency of photoinduced electron–hole pairs, while the enhancement of photocatalytic activity with solar irradiation in the TG was attributed to RGO role, acted as a photosensitizer and a charges separator, simultaneously.
关键词： semiconductors,Solar photocatalysis,photosensitizer,composite materials,charger separator,recombination and trapping
更新于2025-09-23 15:22:29
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Ag2O/TiO2 nanostructures for the photocatalytic mineralization of the highly recalcitrant pollutant iopromide in pure and tap water
摘要： TiO2 was modified by the deposition of Ag2O nanoparticles to increase the photocatalytic degradation of iopromide in water under UV–C (λ = 254 nm) and UV–A/visible light irradiation (380–800 nm) using pure and tap water. Several loadings of Ag2O were deposited on TiO2, namely 0.03, 0.15, 0.25, 0.65, 1.0, 1.15, 1.35 and 1.8 wt. %. XRD, TEM, BET, ICP-OES, XPS, DRS and cathodoluminescence spectroscopy were carried out to characterize the materials, while semiconducting properties of the composite were elucidated through electrochemical and photoelectrochemical characterization. Under UV–C light irradiation, the Ag2O/TiO2 heterostructures showed higher mineralization of iopromide (up to 86%, using the 1.15 wt. % Ag2O/TiO2 material) than unmodified materials (37% for TiO2 and 14% for Ag2O), indicating a synergistic effect by the combination of both compounds in the composite. Under UV–A/visible light irradiation, mineralization achieved with the 1.15 wt. % Ag2O/TiO2 material decreased up to 65%, which was again higher than that obtained for its single components. Stability of the photocatalyst was observed through three consecutive reaction cycles under UV–A/visible light irradiation. In tap water, environmentally relevant concentrations of iopromide were tested (Co = 50 μg L?1), resulting in a high degradation rate, while mineralization dramatically decreased because of the matrix effect. Some by-products were identified by mass spectroscopy and a possible degradation path was proposed. The outstanding photocatalytic activity of the Ag2O/TiO2 materials was explained by the electron trap effect exerted by Ag2O, along with the appearance of different silver species (Ag2O, Ag2O2 and Ag°) throughout the photocatalytic reaction, enhancing the mobility of the charge carriers and thus the generation of reactive species on the photocatalyst surface.
关键词： Semiconductors,X-ray contrast media,Tap water,Photocatalysis,Composite
更新于2025-09-23 15:22:29