Semiconductor Structures Research Articles

Effect of an External Electric Field on the Intracenter Optical Transitions in Quasi-Zero-Dimensional Semiconductor Structures

Effect of an External Electric Field on the Intracenter Optical Transitions in Quasi-Zero-Dimensional Semiconductor Structures

Odd-Even Alkyl Chain Effects on the Structure and Charge Carrier Transport of Two-Dimensional Sn-Based Perovskite Semiconductors.

Oscillations in the chemical or physical properties of materials, composed of an odd or even number of connected repeating methylene units, are a well-known phenomenon in organic chemistry and materials science. So far, such behavior has not been reported for the important class of materials, perovskite semiconductors. This work reports a distinct odd-even oscillation of the molecular structure and charge carrier transport properties of phenylalkylammonium two-dimensional (2D) Sn-based perovskites in which the alkyl chains in the phenylalkylammonium cations contain varying odd and even carbon numbers. Density functional theory calculations and grazing-incidence wide-angle X-ray scattering characterization reveal that perovskites with organic ligands containing an alkyl chain with an odd number of carbon atoms display a disordered crystal lattice and tilted inorganic octahedra accompanied by reduced mobilities. In contrast, perovskites with cations of an even number of carbon atoms in the alkyl chain form more ordered crystal structures, resulting in improved charge carrier mobilities. Our findings disclose the importance of minor changes in the molecular conformation of organic cations have an effect on morphology, photophysical properties, and charge carrier transport of 2D layered perovskites, showcasing alkyl chain engineering of organic cations to control key properties, of layered perovskite semiconductors.

Strain-graded quantum dots with spectrally pure, stable and polarized emission

Structural deformation modifies the bandgap, exciton fine structure and phonon energy of semiconductors, providing an additional knob to control their optical properties. The impact can be exploited in colloidal semiconductor quantum dots (QDs), wherein structural stresses can be imposed in three dimensions while defect formation is suppressed by controlling surface growth kinetics. Yet, the control over the structural deformation of QDs free from optically active defects has not been reached. Here, we demonstrate strain-graded CdSe-ZnSe core-shell QDs with compositionally abrupt interface by the coherent pseudomorphic heteroepitaxy. Resulting QDs tolerate mutual elastic deformation of varying magnitudes at the interface with high structural fidelity, allowing for spectrally stable and pure emission of photons at accelerated rates with near unity luminescence efficiency. We capitalize on the asymmetric strain effect together with the quantum confinement effect to expand emission envelope of QDs spanning the entire visible region and exemplify their use in photonic applications.

Powder x-ray diffraction analysis with machine learning for organic-semiconductor crystal-structure determination

The crystal structure of organic semiconductors is an important factor that dominates various electronic properties, including charge transport properties. However, compared with the crystal structures of inorganic semiconductors, those of organic semiconductors are difficult to determine by powder x-ray diffraction (PXRD) analysis. Our proposed machine-learning (neural-network) technique can determine the diffraction peaks buried in noise and make deconvolution of the overlapped peaks of organic semiconductors, resulting in crystal-structure determination by the Rietveld analysis. As a demonstration, we apply the method to a few high-mobility organic semiconductors and confirm that the method is potentially useful for analyzing the crystal structure of organic semiconductors. The present method is also expected to be applicable to the determination of complex crystal structures in addition to organic semiconductors.

Current-collapse suppression and leakage-current decrease in AlGaN/GaN HEMT by sputter-TaN gate-dielectric layer

In this paper, we explore the electrical characteristics of high-electron-mobility transistors (HEMTs) using a TaN/AlGaN/GaN metal insulating semiconductor (MIS) structure. The high-resistance tantalum nitride (TaN) film prepared by magnetron sputtering as the gate dielectric layer of the device achieved an effective reduction of electronic states at the TaN/AlGaN interface, and reducing the gate leakage current of the MIS HEMT, its performance was enhanced. The HEMT exhibited a low gate leakage current of 2.15 × 10−7 mA/mm and a breakdown voltage of 1180 V. Furthermore, the MIS HEMT displayed exceptional operational stability during dynamic tests, with dynamic resistance remaining only 1.39 times even under 400 V stress.

Spin orbit coupling enhanced thermionic cooling in two-dimensional semiconductor structures

We theoretically investigate the effect of Rashba spin–orbit coupling (RSO) on thermionics properties of two-dimensional semiconductor. Due to the hybridization of parabolic and linear energy dispersion, the thermal energy equipartition is modified. The thermionic emission from the lower spin branch is enhanced and that from the upper spin branch is reduced. For a double quantum well cooling structure under lower doping, the net heat transported through the structure is enhanced by RSO. The coefficient of performance (COP) is improved by about 20% in the low bias regime and around 3% in the high bias regime. Since the RSO can be further tuned by an applied field, the COP can be further optimized.

Inspection techniques in photovoltaic power plants: A review of electroluminescence and photoluminescence imaging

The growth of photovoltaic power plants in both size and number has spurred the development of new approaches in inspection techniques. The most commonly employed methods include visual inspections, current-voltage measurements, infrared thermography, and luminescence imaging. Luminescence, rooted in the electromagnetic radiation capture of semiconductor structures that make up solar cells, proves effective in detecting various failures that may occur throughout the lifespan of a photovoltaic module. This phenomenon can be induced either by injecting current into the photovoltaic module (Electroluminescence) or through optical excitation using an appropriate light source (Photoluminescence). This paper offers an overview of the conventional outdoor luminescence imaging technique, delving into its applications and limitations. Additionally, it provides a comprehensive review of innovative outdoor luminescence technique approaches. These novel techniques aim to address several limitations of conventional methods, such as the considerably lower luminescence emission intensity compared to solar radiation, the need for external energy sources for current injection, the required acquisition time, and the necessity of disconnecting the solar module.

Impact of Solar Cell Infrastructures on Energy Efficiency in Power Grid Integration

Photovoltaic technology harvest electrical energy by stimulating liberated electrons within the semiconductor layers using solar radiation. Photovoltaic technology produces electrical energy by collecting electrons that are liberated in a semiconductor pn-junction by solar radiation. Photovoltaic solar cells have layered semiconductor structures and this study utilised for this objective. Current researches on energy storage with solar cells, focused to optimise the utilisation of the generated energy with cell efficiency. This study offers a thorough analysis of the energy efficiency of solar cells based on their infrastructures. The study involved obtaining computational visuals and doing efficiency verification. This was done by comparing the impact of different chemical structures on energy production. The MATLAB software was used with fixed parameters and varying efficiency. The results show that the Monocrystalline N-Type IBC model exhibits the maximum efficiency in terms of PV cell structure. The MIBC structure is more efficient than polycrystalline cells and also standard monotypes with high temperatures. This allows the cell to reflect itself and passivise the cell base, resulting in a 5% or more increase in energy production. Standard monotype cell has %16.2 efficiency and Monotype IBC has %20.1 efficiency results achieved with PVsyst and Matlab softwares. The results of the calculations were applied in real time and confirmed by testing the impact of structural differences on efficiency with real climate data

Analysis of Frequency and Voltage Dependent Electrical Features of Au/Si3N4/p-GaAs (MIS) Device at Room Temperature

The investigation presented here deals with the comprehensive analysis of the C-V-f and G/ω-V-f characteristics of the Au/Si3N4/p-GaAs (MIS) device. These measurements were performed at 300 K and covered a frequency of between 10 kHz–1 MHz. The determination of the Rs was facilitated by the use of the conductance method, while the evaluation of the Nss of the MIS device was performed according to the Hill-Coleman method. A noteworthy observation concerns the significant frequency dispersion observed in the C-V-f and G/ω-V-f features of the MIS devices, particularly noticeable at low frequencies, which is attributable to the influence of Rs and Nss. Furthermore, the determination of the high-frequency Cm and Gm/ω involved measurements under both reverse and forward-biased conditions, followed by careful adjustments to mitigate the effects of Rs. This meticulous procedure culminated in the derivation of the true capacitance values inherent in semiconductor structure.

Room-temperature spin injection across a chiral perovskite/III-V interface.

Spin accumulation in semiconductor structures at room temperature and without magnetic fields is key to enable a broader range of optoelectronic functionality1. Current efforts are limited owing to inherent inefficiencies associated with spin injection across semiconductor interfaces2. Here we demonstrate spin injection across chiral halide perovskite/III-V interfaces achieving spin accumulation in a standard semiconductor III-V (AlxGa1-x)0.5In0.5P multiple quantum well light-emitting diode. The spin accumulation in the multiple quantum well is detected through emission of circularly polarized light with a degree of polarization of up to 15 ± 4%. The chiral perovskite/III-V interface was characterized with X-ray photoelectron spectroscopy, cross-sectional scanning Kelvin probe force microscopy and cross-sectional transmission electron microscopy imaging, showing a clean semiconductor/semiconductor interface at which the Fermi level can equilibrate. These findings demonstrate that chiral perovskite semiconductors can transform well-developed semiconductor platforms into ones that can also control spin.

Studying mechanism of anisotropic crack generation on C-, R-, A-, and M-planes of sapphire during ultra-precision orthogonal cutting using a visualized slip/fracture activation model

With the growing demand for the fabrication of microminiaturized components, a comprehensive understanding of material removal behavior during ultra-precision cutting has become increasingly significant. Single-crystal sapphire stands out as a promising material for microelectronic components, ultra-precision lenses, and semiconductor structures owing to its exceptional characteristics, such as high hardness, chemical stability, and optical properties. This paper focuses on understanding the mechanism responsible for generating anisotropic crack morphologies along various cutting orientations on four crystal planes (C-, R-, A-, and M-planes) of sapphire during ultra-precision orthogonal cutting. By employing a scanning electric microscope to examine the machined surfaces, the crack morphologies can be categorized into three distinct types on the basis of their distinctive features: layered, sculptured, and lateral. To understand the mechanism determining crack morphology, visualized parameters related to the plastic deformation and cleavage fracture parameters are utilized. These parameters provide insight into both the likelihood and direction of plastic deformation and fracture system activations. Analysis of the results shows that the formation of crack morphology is predominantly influenced by the directionality of crystallographic fracture system activation and by the interplay between fracture and plastic deformation system activations.

Enhanced photocatalytic activity of g-C3N4/Bi2WO6 heterojunction via Z-scheme charge-transfer mechanism

In this study, g-C3N4/Bi2WO6 (CN/BWO) photocatalytic composite materials were prepared using a combination of calcination and solvothermal methods. The coiled sheet CN and the nanosheet BWO are coupled to form Z-scheme semiconductor junctions. For the close alignment between BWO conduction band (CB) and CN valence band (VB), photogenerated electrons originating from the BWO CB readily recombine with holes from the CN VB, which results in the accumulation of photogenerated holes in the BWO VB, exhibiting remarkable oxidation capability, and photogenerated electrons in the CN CB, displaying strong reducibility. This mechanism plays a pivotal role in the generation of ·O2– and ·OH radicals, optimizing the photocatalytic performance. As the atomic proportion of CN/BWO was 9:20, it exhibits a degradation degree of 90.2 % for rhodamine B (RhB) after 60 min illumination, significantly higher than pure BWO (44.0 %). Repetitive experiment results demonstrated the sample's good stability. Additionally, based on electrochemical tests and active species experiment results, the photocatalytic mechanism of the CN/BWO Z-scheme semiconductor structure involving photogenerated charge separation, migration, and photocatalysis was proposed.

The influence of light on transverse magnetoresistance oscillations in low-dimensional semiconductor structures

The influence of light on transverse magnetoresistance oscillations in low-dimensional semiconductor structures

Experimental demonstration of plasmon–plasmon scattering paves the way for electromagnetic wave-based digital logic concept

We report the experimental demonstration of plasmon–plasmon scattering at room temperature in the inversion layer of a patterned metal–oxide–semiconductor structure. This fundamental result paves the way for the development of plasmon–plasmon scattering logic, a revolutionary digital logic concept based on the generation, propagation, and manipulation of plasmons in an electron fluid, which was previously theoretically projected to exhibit femtojoule power dissipations and femtosecond switching speeds, while not demanding expensive nanometer-scale silicon (Si) technology fabrication processes for its implementation.

Stereo-Structural Fine Tuning of Chromaticity.

Lanthanoid carboxylates were synthesized and in situ self-assembled to illustrate temperature-driven evolution in chromaticity. Evolution in structure (crystallinity), composition, luminosity, and chromaticity were investigated revealing the coupled role of divergence in order/structure (spatial organization), and composition in tuning observed color. Loss of crystallinity or increase in residual carbon leads to decrease in luminosity even with increase in hue. Comparing Ho and Er congeners shows that the density of accessible transition states relates to shifts in low and high wavelength components of color. This work demonstrates that, just as interface dipoles can lead to change in semiconductor band gap, structure and composition can analogously alter observed color.

From Bulk to one-dimensional MoS2 nanochains: evolution of electronic, mechanical, and optical properties

We theoretically investigate the stability of a MoS2 nanochain, reporting its electronic, mechanical, and optical properties. The nanochain presents a semiconductor structure with a minute band gap of 67m eV compared to the larger gap bulk and monolayer structures. It is more malleable, enduring a maximum compressive (tensile) strain of 6% (6.5%). It is dynamically stable, showing no negative frequencies along its Brillouin zone (BZ) path. The nanochain is thermally stable at 300K, making it possible to synthesize as a freestanding structure. The optical properties of the bulk, monolayer, and 1D MoS2 materials are evaluated using the time-dependent density functional perturbation theory (TDDFPT) and compared to those determined via the independent particle approximation (IPA). Along the nanochain’s periodic x direction, the reflectivity retains a maximum value of ∼68% in the infrared (IR) region. Furthermore, its optical conductivity also exhibits a peak within the IR regime. These two features make such nanochains suitable as coating materials in applications involving infrared radiation or can even be exploited as conductive substrates in near-IR devices.

Conversion of iron rusty waste into Fe dopant of TiO2 to increase its photocatalytic activity under visible light for photodegradation of rhodamine-B

This present research deals with a systematic study on doping TiO2 with Fe from iron rusty waste to improve the activity under visible light irradiation through gap narrowing in the TiO2 semiconductor structure. The doping was conducted by the sol-gel method by interacting titania tetra isopropoxide (TTIP) with Fe3+ ions dissolved from the iron rusty waste in aqua regia. The concentration of the Fe3+ was varied giving mole ratio to TiO2 as (1:0.04), (1:0.08), (1:0.12), (1:0.16), and (1:0.20). The activity of TiO2–Fe was examined for Rhodamine-B dye photodegradation through batch technique. The influences of the Fe fraction, irradiation time, photocatalyst weight, and solution pH were also evaluated to find the best condition for the dye degradation. The research results attribute that doping TiO2 with Fe3+ from the rusty waste has successfully shifted the band gap energy into the visible regime, which remarkably increases the TiO2 activity under visible light irradiation. The increase is controlled by the Fe fraction in the photocatalyst, and the best performance is shown by TiO2–Fe with a 1:0.12 mol ratio. From the dye photodegradation, it is found that the highest degradation effectiveness (99.20 %) of 5 mg/L Rhodamine B in 50 mL of the solution, can be obtained by using 50 mg of TiO2–Fe (1:0.12), pH 5, in 90 min. The photocatalyst can be reused twice in the photodegradation process without a significant decrease in photoactivity. It is implied that the rusty waste has potential as a Fe dopant source creating a better visible responsive photocatalyst.

Analysis of the Optical Properties and Electronic Structure of Semiconductors of the Cu2NiXS4 (X = Si, Ge, Sn) Family as New Promising Materials for Optoelectronic Devices

In this work, the optoelectronic characteristics of kesterites of the Cu2NiXS4 system (X = Si, Ge, Sn) were studied. The electronic properties of the Cu2NiXS4 (X = Si, Ge, Sn) system were studied using first-principles calculations within the framework of density functional theory. For calculations, ab initio codes VASP and Wien2k were used. The high-precision modified Beke-Jones (mBJ) functional and the hybrid HSE06 functional were used to estimate the bandgap, electronic, and optical properties. Calculations have shown that when replacing Si with Ge and Sn, the band gap decreases from 2.58 eV to 1.33 eV. Replacing Si with Ge and Sn reduces the overall density of electronic states. In addition, new deep (shallow) states are formed in the band gap of these crystals, which is confirmed by the behavior of their optical properties. The obtained band gap values are compared with existing experimental measurements, demonstrating good agreement between HSE06 calculations and experimental data. The nature of changes in the dielectric constant, absorption capacity, and optical conductivity of these systems depending on the photon energy has also been studied. The statistical dielectric constant and refractive index of these materials were found. The results will help increase the amount of information about the properties of the materials under study and will allow the use of these compounds in a wider range of optoelectronic devices, in particular, in solar cells and other devices that use solar radiation to generate electric current.

3D molecular structural modeling and characterization of indium phosphide via irregularity topological indices

Indium phosphide (InP) is a binary semiconductor composed of indium and phosphorus. It has a zinc blende crystal structure, which is a type of cubic lattice structure. This lattice is composed of indium and phosphorus atoms arranged in a lattice of cube-shaped cells, with each cell containing four indium atoms and four phosphorus atoms. This lattice structure is the same for all materials with a zinc blende crystal structure and is the most common type of lattice structure in semiconductors. Indium phosphide (InP) has several chemical applications. It is commonly used as a dopant in the production of semiconductors, where it helps control the electrical properties of the material. InP is also utilized in the synthesis various indium-containing compounds, which can have applications in catalysts and chemical reactions. Additionally, InP nanoparticles have been investigated for their potential use in biomedical imaging and drug delivery systems. The topological characterization of 3D molecular structures can be performed via graph theory. In graph theory, the connections between atoms are represented as edges and the atoms themselves are represented as nodes. Furthermore, graph theory can be used to calculate the topological descriptors of the molecule such as the degree-based and reverse degree-based irregularity toplogical indices. These descriptors can be used to compare the topology of different molecules. This paper deals with the modeling and topological characterization of indium phosphide (InP)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$({\ ext{InP}})$$\\end{document} via degree-based and reverse irregularity indices. The 3D crystal structure of the InP is topologically modeled via partition of the edges, and derived closed form expressions for its irregularity indices. Our obtained results will be surely be helpful in investigating the QSPR/QSAR analysis as well as understanding the deep irregular behavior of the indium phosphide (InP)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$({\ ext{InP}})$$\\end{document}.

Tuning Structure and Properties of a Ferromagnetic Organic Semiconductor via a Magnetic Field-Modified Reduction Process

The development of novel synthesis and assembly strategies is critical to achieving a ferromagnetic organic semiconductor with high Curie temperature. In this study, we report a high magnetic field (HMF)-modified solvothermal approach for the reduction in neutral perylene diimide (PDI) into the dianion species to prepare the PDI magnets comprising radical anions after subsequent oxidation processes. The PDI materials, assembled from the dianion solution by an HMF-modified reduction, exhibit a smaller crystallite size and an enlarged distance of the π-π stacking in the PDI aggregates. Furthermore, the PDI magnets obtained from the process under a 9T field reveal weakened ferromagnetism and the rapid degradation of electrical conductivity compared to those prepared without a magnetic field. Based on spectral and structural characterizations, such performance deterioration originates from the enhanced instability of the radical anions exposed to air, as well as the decreased crystallinity for the radical PDIs synthesized from the HMF-modified reduction process. This work demonstrates that magnetic fields offer an effective way in the material synthesis process to manipulate the structure and magnetic properties of the radical-based organic magnets.