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过滤筛选
- 2018
- computer statistical experiment
- statistical optimization
- resonant-tunneling diode
- negative voltage current differential resistance
- characteristics
- heterojunction
- quantum well
- resonant tunneling border
- Electronic Science and Technology
- Optoelectronic Information Science and Engineering
- Bauman Moscow State Technical University
- V.N. Karazin Kharkiv National University
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Electromodulation of the Negative Differential Resistance in an AlGaAs/GaAs Resonant Tunneling Diode
摘要： In this work, we investigate the impact of the width of the AlGaAs right barrier and the doping concentration in the contact layers on the negative differential resistance (NDR) and the device performance of a double-barrier AlGaAs/GaAs resonant tunneling diode (RTD). Our simulation is performed using a non-equilibrium Green's formalism (NEGF). The obtained results show that increasing the width Lb2 of the right barrier, strongly reduces the peak-to-valley current ratio (PVCR. Especially, it reduces from 2.5 for symmetric RTD AlGaAs (5 nm) / GaAs (5 nm) to 1.1 when the right barrier AlGaAs is equal to 8 nm. Our findings show that a specific width of the right barrier Lb2 = 9 nm exists for which the NDR disappears completely. In addition, an increase in the doping concentration in the contact layers is found to reduce the (PVCR) and, consequently, the (NDR). These results open the door for designing resonant tunneling diodes with suitable negative differential resistances. The simulation of the RTD is performed with the use of Nanohub tools which confirms the various results presented in this paper.
关键词： Schrodinger equation,Resonant tunneling diode,Peak to valley ratio,Current-voltage characteristics,Negative differential resistance
更新于2025-09-19 17:15:36
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Bismuth mediated defect engineering of epitaxial graphene on SiC(0001)
摘要： Structural defects are commonly undesirable in materials, however, atomic-level defect engineering is promising to improve the electronic, mechanical and chemical properties of graphene, if the density and types of defects could be well controlled. Herein, bismuth-mediated defect engineering method for epitaxial graphene (EG) grown on SiC(0001) is demonstrated. It is found that single defects and defect clusters could be facilitated by evaporating Bi atoms on SiC(0001) substrate before the standard EG preparation and, Bi atoms could be thoroughly cleaned away from the EG and the unwanted doping effects of Bi will be avoided by post-annealing at higher temperature. Scanning tunneling microscopy/spectroscopy characterization reveals the atomic structures, the electronic states and the Fermi level shift of flower-like, tube-like and point defects. This study sheds light on the metal-mediated formation of defects in graphene, and provides a practical defect engineering method.
关键词： Defect engineering,Scanning tunneling microscopy/spectroscopy.,Epitaxial graphene (EG)
更新于2025-09-19 17:15:36
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Time domain study on the tunneling dynamics in photoionization microscopy
摘要： The time-dependent wave-packet theory is used to study the tunneling dynamics during the photoionization microscopy in the time domain. The results show both the ionized electron current in the time domain and the radial distribution in the spatial domain originate from two contributions: the quantum tunneling ionization of quasi-bound states and the classical above-barrier ionization of continuous states. The two types of ionization exhibit different temporal characters, resulting in the spatial probability distribution depends on the detection time. For atoms in parallel electric and magnetic fields, the interference narrowing effect is confirmed from the two aspects: the line width evolution and electron current distribution. Tunneling ionization reaches its maximum at the point of levels anti-crossing. This makes it possible to observe node structures in photoionization microscopy of atom or molecule with strong states mixing.
关键词： photoionization microscopy,numerical simulation,tunneling effect
更新于2025-09-19 17:15:36
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Microwave-Assisted Tunneling in Hard-Wall InAs/InP Nanowire Quantum Dots
摘要： With downscaling of electronic circuits, components based on semiconductor quantum dots are assuming increasing relevance for future technologies. Their response under external stimuli intrinsically depend on their quantum properties. Here we investigate single-electron tunneling in hard-wall InAs/InP nanowires in the presence of an off-resonant microwave drive. Our heterostructured nanowires include InAs quantum dots (QDs) and exhibit different tunnel-current regimes. In particular, for source-drain bias up to few mV Coulomb diamonds spread with increasing contrast as a function of microwave power and present multiple current polarity reversals. This behavior can be modelled in terms of voltage fluctuations induced by the microwave field and presents features that depend on the interplay of the discrete energy levels that contribute to the tunneling process.
关键词： Microwave-Assisted tunneling,Single-electron tunneling,Hard-Wall InAs/InP nanowire,Quantum Dots,Coulomb diamonds
更新于2025-09-19 17:13:59
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The Effect of Crystallographic Orientation and Nanoscale Surface Morphology on <i>Poly</i> -Si/SiO <i> <sub/>x</sub></i> Contacts for Silicon Solar Cells
摘要： High-efficiency crystalline silicon (Si) solar cells require textured surfaces for efficient light trapping. However, passivation of a textured surface to reduce carrier recombination is difficult. Here, we relate the electrical properties of cells fabricated on a KOH-etched, random pyramidal textured Si surface to the nanostructure of the passivated contact and the textured surface morphology. The effects of both microscopic pyramidal morphology and nanoscale surface roughness on passivated contacts consisting of a polycrystalline Si (poly-Si) deposited on top of an ultrathin, 1.5–2.2 nm, SiOx layer is investigated. Using atomic force microscopy we show a pyramid face, which is predominantly a Si(111) plane to be significantly rougher than a polished Si(111) surface. This roughness results in a nonuniform SiOx layer as determined by transmission electron microscopy (TEM) of a poly-Si/SiOx contact. Our device measurements also show an overall more resistive, and hence thicker SiOx layer over the pyramidal surface as compared to a polished Si(111) surface, which we relate to increased roughness. Using electron-beam-induced current measurements of poly-Si/SiOx contacts we further show that the SiOx layer near the pyramid valleys is preferentially more conducting, and hence likely thinner than over pyramid tips, edges and faces. Hence, both the microscopic pyramidal morphology and nanoscale roughness lead to nonuniform SiOx layer, thus leading to poor poly-Si/SiOx contact passivation. Finally, we report >21% efficient and ≥80% fill-factor front/back poly-Si/SiOx solar cells on both single-side and double-side textured wafers without the use of transparent conductive oxide layers and show that the poorer contact passivation on a textured surface is limited to boron-doped poly-Si/SiOx contacts.
关键词： passivated contact,tunneling,silicon oxide,electron beam induced current,silicon solar cell,surface orientation,atomic force microscopy
更新于2025-09-19 17:13:59
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Diagnostics of ultra-intense laser pulses using tunneling ionization
摘要： We revisit a recently proposed scheme (Ciappina et al 2019 Phys. Rev. A 99 043405) for accurate measurement of electromagnetic radiation intensities in a focus of high-power laser beams. The method is based on the observation of multiple sequential tunneling ionization of atoms and suggests determination of the peak intensity value from the appearance in the focal area ions with a certain charge number. Here we study the sensitivity of the approach to two essential factors: the focal volume effect and the tunneling ionization model chosen to calculate ionization rates. We show, on the one hand, that the results appear almost model independent for ionization of helium- and hydrogen-like ions and, on the other hand, that the focal averaging leaves the intensity-dependent features visible. Our findings are in favor to a practical implementation of the atomic diagnostics of extreme laser intensities.
关键词： intensity diagnostic,tunneling,extreme light fields,petawatt lasers,strong-field ionization
更新于2025-09-19 17:13:59
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Tunneling-induced broadband and tunable optical emission from plasmonic nanorod metamaterials
摘要： We demonstrate a metamaterial platform for electrically driven broadband light emission induced by electron tunneling. Both the Fabry-Perot and waveguided modes of the metamaterial slab as well the plasmonic mode of the tunneling gap are identified as contributing to shaping the emission spectrum. This opens up an opportunity to design the spectrum and polarization of the emitted light by tuning the metamaterial modes via the geometric parameters of the nanostructure throughout the visible and near-infrared spectral ranges. The efficient coupling of the tunneling-induced emission to the waveguided modes is beneficial for the development of integrated incoherent light sources, while the outcoupled emission provides a source of free-space radiation. The demonstrated incoherent nanoscale light sources may find applications in the development of integrated optoelectronic circuits, optical sensing platforms, imaging, and metrology.
关键词： plasmonics,nanoscale light sources,metamaterials,electron tunneling
更新于2025-09-19 17:13:59
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Nonlinear tunneling effect of snakelike self-similar waves in a grating dual-core waveguide amplifier
摘要： We study on the nonlinear tunneling e?ect of snakelike self-similar waves of the nonlinear Schr¨odinger equation with gains in an asymmetric dual-core waveguide ampli?er with a long-period grating. Using the self-similar transformation we ?nd the bright and dark snakelike self-similar waves with W-, U-, and bell-shaped pro?les. As an application, we investigate the nonlinear tunneling e?ect of these optical structures under some constraint conditions. The results show that the snakelike self-similar waves can similarly pass through the nonlinear barrier or well and can be e?ectively controlled by adjusting the source amplitude and the long-period grating. Our results may have potential applications for improving channel capacity in the graded-index dual-core waveguide ampli?ers with a long-period grating.
关键词： Snakelike self-similar waves,Nonlinear tunneling e?ect,Asymmetric dual-core waveguide ampli?er
更新于2025-09-19 17:13:59
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Imaging doubled shot noise in a Josephson scanning tunneling microscope
摘要： We have imaged the current noise with atomic resolution in a Josephson scanning tunneling microscope with a Pb-Pb junction. By measuring the current noise as a function of applied bias, we reveal the change from single-electron tunneling above the superconducting gap energy to double-electron charge transfer below the gap energy when Andreev processes become dominant. Our spatially resolved noise maps show that this doubling occurs homogeneously on the surface, and also on impurity locations, demonstrating that indeed the charge pairing is not influenced by disruptions in the superconductor smaller than the superconducting coherence length.
关键词： Josephson scanning tunneling microscope,Andreev reflections,current noise,atomic resolution,superconducting gap
更新于2025-09-19 17:13:59
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Interfacial‐Tunneling‐Effect‐Enhanced CsPbBr <sub/>3</sub> Photodetectors Featuring High Detectivity and Stability
摘要： Inorganic halide perovskite (HP)-based photodetectors (PDs) have exhibited fast response speed and high responsivity, but with low detectivity due to the high dark current of devices. Additionally, the intrinsic instability of HPs and interface deterioration originating from ion migration inhibit their practical applications severely. A tunneling organic layer is introduced to solve both these problems. Light-induced charge carriers can flow across the interfacial (poly(methyl methacrylate), PMMA) layer with appropriate thickness via the Fowler–Nordheim tunneling effect. Due to the effective control of dark current, the photo-/dark-current ratio reaches a giant value of 2.13 × 108, and the peak detectivity is as high as 1.24 × 1013 Jones. With such superiority, light signal as weak as 244 pW is accurately imaged by a PD array. Additionally, the hydrophobic organic layer inhibits the destruction of HPs caused by moisture and ion migration induced interface reaction, and negligible response attenuation is observed during continuous work in a humid environment for 48 h. This heterojunction structure design provides a new strategy to enhance the performance and stability of perovskite-based photoelectric and photovoltaic devices.
关键词： tunneling effect,photodetectors,halide perovskites
更新于2025-09-19 17:13:59