Elemental Semiconductors Research Articles

Revisiting semiconductor band gaps through structural motifs: An Ising model perspective

We present an alternative perspective on semiconductor band-gap energies in terms of structural motifs, viewed through the lens of an Ising model as a means of quantifying the corresponding degree of lattice ordering. The validity of the model is demonstrated experimentally first through ${\mathrm{ZnSnN}}_{2}$ as an archetype ternary heterovalent semiconductor, in which variation of cation disorder enables the band gap to be tuned from above its equilibrium phase value, through zero, to negative values which correspond to inverted bands. The model is then applied to example binary compounds InN, GaN, and ZnO where anion-cation antisite defects form the basis for structural motifs, and we present experimental evidence that the same range of band-gap tuning is also possible for such materials. The case of alloys is treated by applying a three-spin Potts model to ${\mathrm{In}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{N}$. The Ising model also applies to elemental semiconductors, and is used to explain the wide range of reported values for silicon and nanoporous graphene in the context of vacancy-based structural motifs.

General-purpose open-source 1D self-consistent Schrödinger-Poisson Solver: Aestimo 1D

We present a general-purpose numerical quantum mechanical solver using Schrödinger-Poisson equations called Aestimo 1D. The solver provides self-consistent solutions to the Schrödinger and Poisson equations for a given semiconductor heterostructure built with materials including elementary, binary, ternary, and quaternary semiconductors and their doped structures. The software can be used to calculate electronic band structures of heterostructures either using a single-band or multi-band k.p envelope function approximation. The software is fully open-source and it is released under the GNU general public license version 3 for full freedom of usage for applications in the fields of nano-electronics, optoelectronics, and solid-state device simulations.

Structural and Electronic Properties of Zigzag Single Wall (8,0), (9,0), and (10,0) Silicon Carbide Nanotubes Sandwiched Between Different Semiconductor and Transition Metal Elements

Using first principles density functional theory calculations, the electronic and geometric structures of three different types of zigzag single wall silicon carbide nano-tubes (ZSSiCNt), (8,0), (9,0), and (10,0), have been studied by sandwiching nano-tubes between different semiconductors, group three elements, and some transition metal elements. When the (9,0) zSSiCNt is sandwiched between different semiconductors, the binding energy (B E ) varies from 2.05 to 5.68 eV/atom. When the (10,0) zSSiCNt is sandwiched between group III elements, the B E varies from 4.35 to 6.89 eV/atom. When the (10,0) zSSiCNt is sandwiched between some transition elements, the B E varies from 1.63 to 5.97 eV/atom. The binding energy variation of SWSiCNT by substituting different elements at the site of carbon and silicon at the end of the zigzag silicon carbide nano-tubes is shown. Substitution of Fe and Ga at the site of Si increases the binding energy to 4.04 eV/atom & 6.32 eV/atom, respectively. The cohesive energy appears to saturate between 6.00 to 6.90 eV, and the stability of different (8,0) SWNt is compared.

A Lossless Passive Snubber Circuit for Three-Port DC–DC Converter

In this article, a soft-switched nonisolated high step-up three-port dc-dc converter is presented for hybrid energy system applications. In the proposed converter, the soft-switching condition is provided for semiconductor elements by a passive lossless snubber without adding any extra active switch or adding any additional semiconductor element in the main power path. The proposed converter is a high integration of single-stage power conversion with multiple input sources and battery port, while the voltage stress of the main switch is kept low. All these benefits have led to high efficiency in comparison to other converter counterparts. Operating principles of the proposed converter are discussed in detail, and design considerations are presented. Finally, experimental verifications are provided to illustrate the feasibility and effectiveness of the proposed converter.

Storage and release of electromagnetic waves using a Fabry-Perot resonator that includes an optically tunable metamirror

We evaluate the transient response of an optically tunable meta-atom composed of an electric inductor-capacitor resonator that is loaded with a piece of high-resistivity silicon and perform a proof-of-concept experiment to demonstrate the storage and release of electromagnetic waves using this meta-atom in the microwave region. The transient time of the meta-atom immediately after commencing laser light illumination of the silicon in the meta-atom is found to be inversely proportional to the incident laser power. The transmittance of the meta-atom at the resonance frequency increases to ten times that obtained without laser illumination at 5.2 ns after the start of laser illumination for a laser power of 1600 mW, a laser spot size of 2 mm $\times$ 1 mm, and a laser wavelength of 447 nm. In contrast, the transient time after turning the laser light off is dependent on the carrier lifetime of silicon and is measured to be several tens of microseconds. Based on the results of evaluation of the transient response of the meta-atom, we propose a method for the storage and release of electromagnetic waves using a Fabry-Perot resonator that includes the meta-atom as one of its mirrors. The electromagnetic wave that is stored in the Fabry-Perot resonator for a few tens of nanoseconds is then successfully released by illuminating the silicon in the meta-atom with the laser light. It is also possible to use this method in the higher frequency region because metamaterials with semiconductor elements can even be used as active metamaterials in the optical region as long as their bandgap energy is higher than the signal photon energy.

Material property effect on conical semiconductor element temperatures in inhomogeneous thermoelectric coolers

The temperature-dependent material property effects, including the thermal conductivity, Seebeck coefficient, and electrical resistivity, on the thermoelectric element (TE) temperature profiles are assessed in this study. The nonlinear partial differential equation governing energy transport within a one-dimensional TE is solved using a finite difference method. The solution of the TE temperature field is obtained by solving the resulting finite difference equation in the form of a third-order polynomial. The effects of key variables on the cooling process are discussed using a practical example. Results indicate that internal constrictive resistance and Joule heat generation can be reduced with conical elements when compared to conventional free-standing elements. The cooling efficiency can be improved by incorporating a temporarily transient current pulse before it reaches a steady-state condition. This additional transient cooling and steady-state recovery time strongly depend on the magnitude of the current pulsed, duration, and pulse shape, as well as material properties. Strategies for cooling are investigated in this study; the knowledge gained from this study can be utilized by engineers in the thermoelectric industry for design optimization.

Thermal performance evaluation of a thermoelectric cooler coupled with corona wind

The performance of a heat dissipation system that consists of a thermoelectric cooler (TEC) and corona wind generator is investigated. The combined thermoelectric cooling and corona discharge power on the system performance are explored via experiment and analytical analysis. The corona wind cooling system is optimized to achieve a higher corona wind velocity. Utilizing the TEC operating temperature, corona wind velocity, and power consumption, the study reveals that the proposed cooling system efficiency can be improved with an increase in these physical parameters. However, its performance reaches an optimal value once the Fourier conduction became a dominate factor when compared to the Peltier and Joule heating effects within the semiconductor elements of a TEC. Considering the cooling effect and power consumption, the optimal TEC and corona discharge power are determined to both be 1 W. The COP value of the proposed coupling system and the decrease of temperature are found to increase by 39.5% and 40%, respectively, indicating that the cooling efficiency of the system is improved after coupling. The knowledge gained from this study will provide a better understanding of various system parameters, including cooling temperature, power consumption and flow velocity in thermal management technology, as they are closely related in the field of electronic cooling system design.

Josephson current mediated by ballistic topological states in Bi2Te2.3Se0.7 single nanocrystals

Superconducting proximity devices using low-dimensional semiconducting elements enable a ballistic regime in the proximity transport. The use of topological insulators in such devices is considered promising owing to the peculiar transport properties these materials offer, as well the hope of inducing topological superconductivity and Majorana phenomena via proximity effects. Here we demonstrate the fabrication and superconducting properties of proximity Josephson devices integrating nanocrystals single of Bi2Te2.3Se0.7 with a thickness of a few unit cells. Single junctions display typical characteristics of planar Josephson devices; junctions integrating two nanocrystals behave as nanodimensional superconducting quantum interference devices. A peculiar temperature and magnetic field evolution of the Josephson current along with the observed excess current effect point towards the ballistic proximity regime of topological channels. This suggests the proposed devices are promising for testing topological superconducting phenomena in two-dimensions.

Device Postannealing Enabling over 12% Efficient Solution-Processed Cu2 ZnSnS4 Solar Cells with Cd2+ Substitution.

Kesterite Cu2 ZnSnS4 is a promising photovoltaic material containing low-cost, earth-abundant, and stable semiconductor elements. However, the highest power conversion efficiency of thin-film solar cells based on Cu2 ZnSnS4 is only about 11% due to low open-circuit voltage and fill factor mainly caused by antisite defects and unfavorable heterojunction interface. In this work, a postannealing procedure is proposed to complete a Cd-alloyed Cu2 ZnSnS4 device. The postannealing to complete the device significantly enhances the performance of the indium tin oxide and promotes the moderate interdiffusion of elements between the layers in the device. As a result of the diffusion of Cu, Zn, In, and Sn, the interfacial electron and hole densities are improved, leading to the achievement of a suitable band alignment for carrier transport. The postannealing also reduces the interface traps and deep-level defects, contributing to decreased nonradiative recombination. Therefore, the open-circuit voltage and fill factor are both improved, and an efficiency over 12% for pure sulfide-based kesterite thin-film solar cells is obtained.

The Results of Simulation of the process of occurrence of damages to the Semiconductor Elements of Radio-Electronic Equipment under the influence of Multi-Frequency Signals of Short Duration

The Results of Simulation of the process of occurrence of damages to the Semiconductor Elements of Radio-Electronic Equipment under the influence of Multi-Frequency Signals of Short Duration

Carrier-trapping induced reconstruction of partial-dislocation cores responsible for light-illumination controlled plasticity in an inorganic semiconductor

Inorganic semiconductors show interesting mechanical behavior in response to their surrounding lighting environments. In fact, we recently found out that zinc sulfide (ZnS) shows the light-illumination controlled plasticity at room temperature. However, its mechanism is poorly understood. Here we report systematic density functional theory results of electronic and atomic structures of glide partial dislocations in ZnS. We have revealed that partial dislocations in ZnS have excess electrostatic fields localized around their cores and can trap electrons or holes, depending on excess ionic species at the cores. Such carrier-dislocation interactions can induce energetically more stable bond reconstruction at their cores, as compared with the case before carrier trapping. Reconstructed bonds at the dislocation cores should be broken upon dislocation glide, and thus can restrict the dislocation motion significantly. Such reduced dislocation motion due to core reconstruction should give rise to increased plastic deformation stresses, namely, hardening of the materials under light illumination. The present results provide a critical understanding of the experimentally observed light-illumination controlled plasticity in ZnS at the electronic level, which is opposed to previously reported plasticity and dislocation motion in other elemental and III-V semiconductors.

Thickness Optimization of ZnO/CdS/CdTe Solar Cell by Numerical Simulation

CdTe based solar cells with high efficiency alternative to solar cells from elemental semiconductors is an important work carried out over the decades. However, the research has not yet yielded the highest possible efficiency with CdTe absorber. Selection of suitable window layer and optimizing the thickness of the different layers is still a quest in researchers. Numerical simulation of the different material combinations can speed up the research work. In this regard, numerical simulation is an essential tool to find the optimized structure for the enhanced device performance. In the present work, the thicknesses of window and absorber layers, one of the crucial factors that affect the solar cell performance, are tuned for ZnO/CdS/CdTe system. In case of CdS/CdTe solar cells, spectral loss created by CdS lowers the cell efficiency. Concept of bilayer window is useful to minimize the loss at window layer. Hence the ZnO/CdS bilayer window is adopted and demonstrated that the cell efficiency can be increased up to 17.66% with current density of 28.4 mA/cm2 and 73.7% fill factor.

THE RESULTS OF SIMULATION OF THE PROCESS OF OCCURRENCE OF DAMAGES TO THE SEMICONDUCTOR ELEMENTS UNDER THE INFLUENCE OF MULTI-FREQUENCY SIGNALS OF SHORT DURATION

In articles questions of occurrence of damages in semiconductor elements at influences on them of multi-frequency space-time signals (MF STS) are considered. The studies to improve the affection accumulation method for the case of influence to the semiconductor element base by the multi-frequency space-time signals have been conducted. The estimates of the probability of affection of the semiconductor element under the influence of the multi-frequency space-time signals have been obtained. As a result of the researches conducted, the method of affection accumulation for the case of the influence of MF STS on the semiconductor element base has been improved. This method involves the usage of statistical characteristics of thermal energy to estimate the probability of degradation of the p-n junctions for normal (diodes, transistors) and equable (integrated circuits) distribution laws. The results of modelling the calculation of the probability of damage to semiconductor elements of electronic equipment under the influence of multi-frequency signals of short duration are presented.

Magnetotransport properties of tellurium under extreme conditions

This study investigates the transport properties of a chiral elemental semiconductor tellurium (Te) under magnetic fields and pressure. Application of hydrostatic pressure reduces the resistivity of Te, while its temperature dependence remains semiconducting up to 4 GPa, contrary to recent theoretical and experimental studies. Application of higher pressure causes structural as well as semiconductor-metal transitions. The resulting metallic phase above 4 GPa exhibits superconductivity at 2 K along with a noticeable linear magnetoresistance effect. On the other hand, at ambient pressure, we identified metallic surface states on the as-cleaved ($10\overline{1}0$) surfaces of Te. The nature of these metallic surface states has been systematically studied by analyzing quantum oscillations observed in high magnetic fields. We clarify that a well-defined metallic surface state exists not only on chemically etched samples that were previously reported, but also on as-cleaved ones.

Interleaved Ultrahigh Step-Down Converter With Low Component Count

An ultrahigh step-down converter with a low number of semiconductor devices is presented in this article. Important features of this converter are simple structure with low size and cost, low voltage and current stress on components, low output current ripple, and low conduction and switching losses. In this converter, the power switches are turned on under zero current switching (ZCS) condition, whereas the output diodes commutate under ZCS condition without any auxiliary circuit. Thereby, in addition to the converter efficiency improvement, the diodes reverse recovery problem is alleviated. The proposed topology has employed a two-phase interleaved structure to reduce current stress, three windings coupled inductors to further decrease the voltage gain, and two series capacitors to diminish the voltage stress on the semiconductors elements and recover the leakage inductances energy. The experimental results of an implemented prototype are provided to evaluate the effectiveness of the proposed topology at 100 kHz and 200 W, which converts a 400-V input voltage into a 12-V output voltage.

THE ROLE OF STATIC VAR COMPENSATOR AT REACTIVE POWER COMPENSATION

The need for electricity is increasing and the cost of energy generation is arising. For this reason, it is important to use the generated energy in good quality, safely and efficiently. Reactive power compensation is one of the most effective application to reduce transmission losses, prevent voltage drops, prevent consumers from paying for reactive energy, facilitate operating, increase efficiency and save energy in energy systems. However, due to improvements in semiconductor technology, reactive power compensation systems have gained a new dimension. The power compensation made by the use of semiconductor power elements is called Static VAr Compensation. This compensation is used for the compensation of loads such as arc furnaces, elevators, automotive; paper packaging, food and textile, point welding machines, port cranes, flat welds. Transient events are minimized, losses are reduced, back up possibility, control flexibility and reliability are ensured by using Static VAr Compensation systems in power network. In this study, thyristor triggering angles and power factor values of a system, that contains reactive loads and controlled by Static VAr Compensation, were obtained by using the computer software developed by Microsoft C Sharp (C#) programming language. The results were discussed in terms of importance of using such controlling structures in power networks.

The method of determining the Probability of Affection of the Semiconductor Elements under the influence of the Multifrequency Space-Time Signals

The method of determining the Probability of Affection of the Semiconductor Elements under the influence of the Multifrequency Space-Time Signals

Magnetotransport signatures of Weyl physics and discrete scale invariance in the elemental semiconductor tellurium

The study of topological materials possessing nontrivial band structures enables exploitation of relativistic physics and development of a spectrum of intriguing physical phenomena. However, previous studies of Weyl physics have been limited exclusively to semimetals. Here, via systematic magnetotransport measurements, two representative topological transport signatures of Weyl physics, the negative longitudinal magnetoresistance and the planar Hall effect, are observed in the elemental semiconductor tellurium. More strikingly, logarithmically periodic oscillations in both the magnetoresistance and Hall data are revealed beyond the quantum limit and found to share similar characteristics with those observed in ZrTe5 and HfTe5 The log-periodic oscillations originate from the formation of two-body quasi-bound states formed between Weyl fermions and opposite charge centers, the energies of which constitute a geometric series that matches the general feature of discrete scale invariance (DSI). Our discovery reveals the topological nature of tellurium and further confirms the universality of DSI in topological materials. Moreover, introduction of Weyl physics into semiconductors to develop "Weyl semiconductors" provides an ideal platform for manipulating fundamental Weyl fermionic behaviors and for designing future topological devices.

ПОРІВНЯЛЬНИЙ АНАЛІЗ ПАСИВНИХ, АКТИВНИХ ТА ГІБРИДНИХ ФІЛЬТРІВ ГАРМОНІК СТРУМУ ДЛЯ ЧАСТОТНО-РЕГУЛЬОВАНОГО ЕЛЕКТРОПРИВОДУ

The analysis of three types of harmonic filters of the mains current used in power supply systems of asynchronous electric drives with frequency control is carried out. Mathematical modeling of a typical version of such a system is carried out, supplying an electric drive with a capacity of 250 kW from an industrial network of 0.4 kV, 50 Hz. The spectrograms and diagrams of the current of the active and hybrid filters are compared and significant differences in the values ​​of the transistor currents necessary for the same level of harmonic suppression are determined. The main factors affecting the pricing and optimization of reactive and semiconductor elements are described. A significant effect of the relationship between the reactivity of the short circuit of the network and the additional reactor of the hybrid filter on its efficiency and cost has been established. References 11, Figures 6, Table 1.

Electronegativity and doping in Si1-xGex alloys

Silicon germanium alloys are technologically important in microelectronics but also they are an important paradigm and model system to study the intricacies of the defect processes on random alloys. The key in semiconductors is that dopants and defects can tune their electronic properties and although their impact is well established in elemental semiconductors such as silicon they are not well characterized in random semiconductor alloys such as silicon germanium. In particular the impact of electronegativity of the local environment on the electronic properties of the dopant atom needs to be clarified. Here we employ density functional theory in conjunction with special quasirandom structures model to show that the Bader charge of the dopant atoms is strongly dependent upon the nearest neighbor environment. This in turn implies that the dopants will behave differently is silicon-rich and germanium-rich regions of the silicon germanium alloy.