Elemental Semiconductors Research Articles

SIMULATION OF THE P-I-N-STRUCTURES CHARACTERISTICS INTERACTING WITH HIGH-FREQUENCY ELECTROMAGNETIC RADIATION BY PERTURBATION THEORY METHODS

The mathematical model is proposed for the electron-hole plasma characteristics predicting of the active region (i-region) of p-i-n structures, taking into account the effect of the displacement current (induced by an external microwave electromagnetic field) on the formation of a space charge. The model is based on a singularly perturbed nonlinear boundary value problem for the system of the electron-hole current continuity equations and Poisson’s (the Poisson’s equation contains a naturally formed small parameter). The model nonlinear boundary value problem is reduced to a recurrent sequence of linear boundary value problems for determining of the electron-hole plasma concentrations and the electric potential distributions in the i-region by using asymptotic methods, in particular, the boundary layer method and complex amplitudes. The proposed mathematical model feature is that it reflects the role of the boundary layer in the p-i-n structure contact zones in the formation of a space charge and takes into account the effect of a displacement current caused by microwave radiation. An algorithm for predicting the charge carrier concentrations distribution in the electron-hole plasma is constructed. It is shown that an extraneous microwave field entails an additional increase in the stationary concentration of electrons and holes in the active region, against which the plasma concentration fluctuates at the microwave field frequency (the appearance of higher harmonics is not taken into account in the model). The effect of the growth of the concentration stationary component is more pronounced in the zones of p-i-, n-i-contacts. The proposed mathematical model and the developed algorithm for analyzing the problem posed are important for developers of microwave electronics semiconductor elements, in particular, p-i-n structures used for switching powerful electromagnetic fields and as protective devices for the input paths of radio engineering systems.

In situ integration of Te/Si 2D/3D heterojunction photodetectors toward UV-vis-IR ultra-broadband photoelectric technologies.

Over the past decade, 2D elemental semiconductors have emerged as an ever-increasingly important group in the 2D material family due to their simple crystal structures and compositions, and versatile physical properties. Taking advantage of the relatively small bandgap, outstanding carrier mobility, high air-stability and strong interactions with light, 2D tellurium (Te) has emerged as a compelling candidate for use in ultra-broadband photoelectric technologies. In this study, high-quality centimeter-scale Te nanofilms have been successfully produced by exploiting pulsed-laser deposition (PLD). By performing deposition on pre-patterned SiO2/Si substrates, a Te/Si 2D/3D heterojunction array is formed in situ. To our delight, taking advantage of the relatively small bandgap of Te, the Te/Si photodetectors demonstrate an ultra-broadband photoresponse from ultraviolet to near-infrared (370.6 nm to 2240 nm), enabling them to serve as important alternatives to conventional 2D materials such as MoS2. In addition, an outstanding on/off ratio of ∼108 and a fast response rate (a response/recovery time of 3.7 ms/4.4 ms) are achieved, which is associated with the large band offset and strong interfacial built-in electric field that contribute to suppressing the dark current and separating photocarriers. Beyond these, a 35 × 35 matrix array has been successfully constructed, where the devices exhibit comparable properties, with a production yield of 100% for 100 randomly tested devices. The average responsivity, external quantum efficiency and detectivity reach 249 A W-1, 76 350% and 1.15 × 1011 Jones, respectively, making the Te/Si devices among the best-performing 2D/3D heterojunction photodetectors. On the whole, this study has established that PLD is a promising technique for producing high-quality Te nanofilms with good scalability, and the Te/Si 2D/3D heterojunction provides a promising platform for implementing high-performance ultra-broadband photoelectronic technologies.

Improving Humidity Sensing of Black Phosphorus Nanosheets by Co-Doping Benzyl Viologen and Au Nanoparticles

Black phosphorus (BP) is a two-dimensional and layered elemental semiconductor that is very sensitive to the subtle fluctuation of relative humidity (RH). However, the practical application of BP material was undesirably plagued by the irreversible degradation under moisture/oxygen atmospheres. To circumvent this limitation, here we prepared BP co-doped with benzyl viologen (BV) and Au nanoparticles as the sensing layer and explored the humidity-sensing performance at room temperature (20 °C). Unlike BP (BP-BV) counterparts, BP-Au (BP-BV-Au) sensors demonstrated unvaried response polarity with increasing RH. And BV introduction improved the recovery characteristics. Additionally, the ternary BP-BV-Au sensors delivered decent selectivity and negligible hysteresis. On the one hand, the in situ reduction of Au nanoparticles consumed lone electron pairs within BP, suppressed the interaction with ambient moisture/oxygen, and improved the operation stability and recovery. On the other hand, hydrophobic BV as the protection layer further hindered water attachment. This co-doping behavior reduced the hole density and ensured the predominant interaction between low-energy sorption sites within BP and water molecules, thus leading to a larger resistance modulation (i.e., stronger response) and quicker reaction kinetics. This work offered a feasible method to propel the practical application and enriched the sensing mechanisms of BP-based humidity sensors.

Increasing power of generator on nonlinear magnetic nanostructure

Background: One of the most promising areas of development of modern electronics is the creation of spintronic devices, which should replace the traditional semiconductor elements. The use of electron spin as a carrier of information in magnetic nanostructures can radically change modern life. Objectives: The aim of this work is to find ways to increase the power of the generator on the magnetic nanostructure by changing its electrical circuit and more optimal external electromagnetic parameters that affect the state of electrons in the studied layered structure. Materials and methods: The solution of this problem is carried out by numerical simulation of the magnetic nanostructure using a specially created micromagnetic simulator, which implements an algorithm for the simultaneous solution of the system of Maxwell and Landau-Lifshitz-Hilbert equations. The solution of such a complex problem is accelerated by the use of a quasi-static approximation in solving the system of Maxwell's equations, which is justified by the small size of the calculation area compared to the depth of the skin layer. Further calculations of the electrodynamic system are performed using the finite element method. To obtain the best frequency and energy parameters of the generator, it is proposed to introduce a resonant circuit to the schematic diagram of the studied generator, which is excited by short nanosecond pulses. Results: A scheme of a generator on a magnetic nanostructure containing a resonator with concentrated parameters is proposed, and a system of nonlinear integro-differential equations with respect to electric currents is obtained in general. Numerical calculation of this system includes, in addition to the calculation of the scheme, also the modeling of a nonlinear electrodynamic structure by the finite element method. The energy and spectral characteristics of the studied generator are obtained. The search for the optimal values of the geometric parameters of the nanostructure and the magnitude of the external longitudinal magnetization is carried out. Conclusions: Due to the complex nature of nonlinear processes in the magnetic nanostructure, the use of an external resonator, which could improve the spectral parameters of the generated current, did not give a noticeable improvement. The influence of the value of the external magnetization on the output power of the generator is complex and nonlinear, but, in general, a decrease in the level of magnetization leads to a significant decrease in power. It is established that the thickness of the magnetic layer of 6 nm is optimal for improving the energy characteristics of the generator.

Understanding Thermal Lagging Behaviors in Thermoelectric Elements With the Dual-Phase-Lag Model

Abstract This study investigates the heat transport mechanism in semiconductor elements within a homogeneous thermoelectric cooling system using the dual-phase-lag (DPL) model. The thermal lagging behavior is analyzed and explored during the energy transport process. The coupled energy and constitutive partial differential equations are solved simultaneously to reduce the complexity of the high-order spatial and time derivatives. This approach simplifies the mathematical solution process and reduces numerical instabilities when compared to the conventional methodology in which either the temperature or heat flux is solved individually with a single equation. The effect of the thermal lagging behavior on energy transport is examined and compared to results by using the Cattaneo–Vernotte model. Furthermore, the phase-lag behavior on the temperature and heat flux profiles is investigated in detail. This study provides perceptive information for engineering applications in which the microscale heat transport phenomenon plays a significant role during the design process. Adding the dual-phase-lag model to the traditional heat diffusion model is a complementary option for engineers in the thermoelectric industry.

Control of thermal regime of thermoelectric coolers inuniform temperature field

The possibility of using a complex of thermoelectric coolers to control the thermal regime of heat-loaded elements of radio electronic equipment, the parameters of which significantly depend on the temperature conditions of operation, is considered.The analysis was carried out for conditions of the same level of cooling of semiconductor elements for typical temperature drops, rangeof dissipation power, current modes of operation, and geometry of thermoelement legs.It is shown that it is rational to use distributed active cooling systems to ensure the required thermal regime of spatially distributed heat-loaded elements with different dissipation power. To ensure the required thermal conditions, it is proposed to use both individual and group variants of the structure layout: heat-loaded element-thermoelectric cooler-radiator.The developed mathematical models of the relationship between the number of thermoelements and the thermal load, the power consumption with the temperature difference and the operating current are analyzed. Models of the main operational characteristics of coolers that are significant for control systems are presented: the relative failure rate and the time to reach a stationary mode.The results of calculations of the main parameters, reliability indicators and dynamic characteristics for an individual version of the layout of thermoelectric coolers with different dissipation power and current operating modes are presented. The group diagram of the arrangement of the object-cooler with series connection and located on the same heat sink and their comparative analysis is considered. When choosing the current mode, it is necessary to take into account the mutual influence and weight of each of the limiting factors, by varying which, when designing the complex and thermoelectric coolers, it is possible to choose compromise modes of operation.

Features of the MBE growth of nanowires with quantum dots on the silicon surface

The development of a new semiconductor element base is necessary to create a new generation of applications. At present time, the synthesis of high-quality hybrid nanostructures based on III-V quantum dots in the body of nanowires of a wide range of material systems is an urgent and important task. In work hybrid III-V nanostructures based on QDs in the body of NWs in GaP/GaAs and AlGaP/InGaP material systems were synthesized in on silicon substrates and their physical properties were investigated.

Self-Catalytic Growth of Elementary Semiconductor Nanowires with Controlled Morphology and Crystallographic Orientation.

While the orientation-dependent properties of semiconductor nanowires have been theoretically predicted, their study has long been overlooked in many fields owing to the limits to controlling the crystallographic growth direction of nanowires (NWs). We present here the orientation-controlled growth of single-crystalline germanium (Ge) NWs using a self-catalytic low-pressure chemical vapor deposition process. By adjusting the growth temperature, the orientation of growth direction in GeNWs was selectively controlled to the ⟨110⟩, ⟨112⟩, or ⟨111⟩ directions on the same substrate. The NWs with different growth directions exhibit distinct morphological features, allowing control of the NW morphology from uniform NWs to nanoribbon structures. Significantly, the VLS-based self-catalytic growth of the ⟨111⟩ oriented GeNW suggests that NW growth is possible for single elementary materials even without an appropriate external catalyst. Furthermore, these findings could provide opportunities to investigate the orientation-dependent properties of semiconductor NWs.

Characteristic evaluation of a simple hand-made semiconductor dosimeter for mammography

Daily quality control of mammography equipment is important for providing optimal images and determining appropriate doses. To popularise dosimeters, the Measurement Division, the Japanese Society of Radiological Technology hold a seminar on making simple dosimeters. At this seminar, a hand-made dosimeter for mammography (HD-M) can be made at low cost. However, HD-Ms employ semiconductors, and their energy responses are subject to significant variations. This investigation involved the determination of precautions when using HD-Ms, examining their energy response characteristics and measurable energy ranges. HD-M has four types of selectors for response correction. When the selector and the tube voltage were equal, the HD-M readings matched that of the ionisation chamber within 5%. However, in case of target filter combinations and measuring tube voltages that the selector does not support, the HD-M readings differed by up to 53% from the ionisation chamber values. HD-M may use different measurement circuits and semiconductor elements depending on the time of the seminar. In this study, it was clarified that the correction factor k, which is the average value of the ratio of the measured value of the ionisation chamber dosimeter to the measured value of HD-M, changes from 0.62 to 1.53 depending on irradiation conditions such as the combination of target filters and the tube voltage. It was demonstrated that HD-M functions sufficiently as a dosimeter for daily management by determining the correction factor using the method proposed in this study.

Carbon Surfaces Doped with (Co3O4-Cr2O3) Nanocomposite for High-Temperature Photo Thermal Solar Energy Conversion Via Spectrally Selective Surfaces

Invention new thin films nano-coating to obtain high-level performance spectrally selective surfaces to enhance solar energy by spin and casting methods, thin films coating are deposited by these techniques on aluminum and glass substrates that were pre-cleaned. Nanocomposite thin film coating comprising (Co3O4:Cr2O3) and carbon to gain an economical coating. The coating has a high absorptivity of solar energy. Nanomaterials have been used in various concentration ratios to dope carbon, and Energy Dispersive Analysis (EDX) was used to determine carbon ash's chemical composition; SEM measured its practical size. Optical properties have been studied by the UV-Visible Spectra and reflectivity tests in a range from 250-1300 nm at room temperature. Absorbance coefficient, transmittance, reflectance, skin depth, optical density, optical energy gap (Eg), and Urbach energy of nanocomposite thin films have also been specified. The Eg of doped C has been measured with different concentration ratios of (Co3O4:Cr2O3) such as sample F (0.5:2.5/7), sample G (1:2/7), sample H (1.5:1.5/7), the sample I (2:1/7), and sample K (2.5:0.5/7) wt. %, the concentration of C is fixed for all samples (7) wt. %. The results revealed that the Eg is ranged (2.9-3.9 eV) and the absorptivity in the ranged (88-93.2 %) for all doped samples. The absorptivity values of nanocomposites are very close to semiconductor elements, which have high absorptivity to the wavelength intensity. The synthesized coating will be used over a flat plate collector as a trap to absorb solar energy for a highly feasible selective surface.

The Effects of Filter Capacitors on Cable Ripple at Different Sections of the Wind Farm Based Multi-Terminal DC System

In most DC power systems, power electronic devices can introduce ripple content into the DC grid, where large input ripple currents on the DC link can have a negative influence. Under these circumstances, DC side filters play an important role in the reduction of ripple content. In this paper, based on a full detailed closed loop model of the entire offshore wind farm multi-terminal DC network, the effect of filter capacitors connected at different sections of the system on the limitation of the AC ripple content, particularly in the DC cables, is studied. In contrast to other work on HVDC for offshore wind, where simplified or equivalent circuits are mainly used while concentrating on the power and control system, this study can be regarded as the specific study of filter capacitors operating within a detailed system model. Utilising the advantages of PLECS, which is a highly effective tool in the simulation of power electronic circuits, no small-signal or simplified equivalent models are used in the system, and the entire study is based on detailed and accurate models of the semiconductor elements and transformers, which help to provide more realistic simulation results and a better understanding of the system. Another novel point in this paper is a new concept, relative losses, which is proposed to simplify extensively the calculation of losses in this research. Finally, the size of the filter capacitors at different sections of the system under different situations is suggested.

Residual stress and thermal properties of rubber‐modified epoxy systems for semiconductor package

AbstractThe thermal and mechanical breakage of epoxy coating due to easy cracking, poor toughness, and large residual stress, occurring during curing and thermal aging process, is the key factor responsible for damage of silicon device on semiconductor elements. In this study, modified epoxy resins containing an imide ring and polybutadiene rubber‐modified epoxy resin used as the toughening agents were prepared to investigate the residual stress generated during the curing and thermal aging process. The curing process and the thermal properties of the modified epoxy systems were assessed by differential scanning calorimetry and rotational rheometry, dynamic thermomechanical analysis, thermomechanical analysis, and thermogravimetric analysis. A thin film stress analyzer was used to analyze the changes in thermal stress of the modified epoxy systems during curing and cyclic stress and compared with the data from theoretical calculation. The results show that, with the increase in content of the toughening agent, the toughness of the modified epoxy systems was significantly improved, and the curing and thermal cycle stresses could be simultaneously reduced. Besides, we also envision the extension of the comprehensive evaluation method for residual stress described in this study to enable the modification of epoxy coatings prepared using a toughening agent, in the near future.

Transformer-Less Switched-Capacitor Quasi-Switched Boost DC-DC Converter

In this article, a quasi-switched boost converter based on the switched-capacitor technique with high step-up voltage capability is dealt with and analyzed. The proposed converter offers a simple structure and low voltage stress on the semiconductor elements with intrinsic small duty cycle. An inductor of the proposed converter is connected in series with the input voltage source; therefore, continuous input current ripple is attainable. In addition, the efficiency of the proposed converter is also improved. A detailed steady-state analysis is discussed to identify the salient features of the switched-capacitor-based quasi-switched boost DC-DC converter. The performance of the converter is compared against similar existing high boost DC-DC converters. Finally, the switched-capacitor-based quasi-switched boost DC-DC converter is investigated by experimental verification.

Thermoelectric modular systems based on semiconductor elements of Peltier-Seebeck for vehicles

Elevations in technology of semiconductor materials allow for new vehicle systems use for improvement in the standard ones. One of the most promising materials for achieving an efficacy of more than 50% is polyaniline, which belongs to the class of conductive polymers that has semiconducting peculiarities. For instance, a new generation of semiconductor elements based on the Peltier-Seebeck effect makes it possible to use them to create thermoelectric generators, which means to use the thermal energy of the exhaust gases of internal combustion engines (ICE) to generate electrical power. The second area where Peltier-Seebeck semiconductor elements find application in automobiles are modular climate control systems. Due to the absence of moving parts and relatively small dimensions, they allow the creation of individual climatic zones in the car interior. An elegant design and technological solution is the placement of similar thermal semiconductor modules inside the driver’s and passenger’s seats, which makes it possible to transfer heat more efficiently and make climatic zones more apparent. The article considered engineering options for the design of climate control units based on Peltier elements and the creation of a prototype. The issues of integration into the vehicle on-board network and the features of power control are considered. The studies and results of this paper can contribute to improving the energy efficiency and technosphere safety of vehicles.

Intracenter dipole transitions of a hydrogen-like boron acceptor in diamond: Oscillator strengths and line broadening

Substitutional boron in diamond acts as an acceptor center with the ionization energy of about 372 meV. Unlike its analogues in elemental semiconductors (silicon, germanium), boron bound states are poorly described by the electronic mass approximation due to the large ionization energy and the small spin-orbit splitting of the valence band in diamond. Thereby experimental investigations appear to be a main way of study of discrete electronic states of boron in diamond.In this paper, we report infrared (IR) absorption spectroscopy results obtained for HPHT-grown single crystal diamonds doped with natural boron (80% 11B – 20% 10B), and with isotopically enriched boron (99% 11B – 1% 10B). A moderate dopant concentration (1016–1017 cm−3), low concentration of lattice defects and vanishing thermal impact at cryogenic temperatures provided significantly reduced line broadening so that more than 60 boron transitions could be spectrally resolved. Mathematical approximation of the spectral lines revealed the main empiric features of zero-phonon dipole intracenter transitions: their energy, linewidth and integrated absorption. This allowed us to calculate oscillator strength of the boron acceptor transitions in diamond. The Lorentzian shape of the spectral lines indicates dominating uniform broadening of the transitions. Together with the relatively broad linewidths (0.1–0.5 meV) it reveals strong electron-phonon interaction in boron-doped diamond.

A New Modular Structure of Marx Generator Based on Interleaved Boost Converter Operating in Discontinuous Conduction Mode

In this article, a new modular structure of Marx generators (MGs) based on interleaved boost converter is proposed. The converter operates in discontinuous conduction mode to generate a high-voltage pulsed power with a common low-voltage source. Unlimited stages can be added to the proposed structure to reach lower maximum voltage stress for the semiconductors or to generate several kilovolts of the output pulses, while the voltage of the semiconductors remains constant. This structure resulted in a higher pulse repetition rate, fewer semiconductor elements, and lower semiconductor voltage stress in comparison to conventional MGs. Hence, the proposed structure is applicable for and efficient in supplying plasma applications with high-voltage pulses. The theoretical foundation of the introduced converter is presented and its performance is simulated using OrCAD software. Based on the obtained results, the maximum voltage of the output pulse is 40 times the input voltage in a single-stage structure. An 80-W prototype of the proposed structure was built to validate the accuracy of the theoretical foundation and the simulation results.

Effective prevention of charge trapping in red phosphorus with nanosized CdS modification for superior photocatalysis

The hydrothermal-treated red phosphorus (HRP) is a visible light response element semiconductor. However, photoelectrons and holes to recombine easily due to its narrow band gap. A CdS/HRP hierarchical heterostructure was designed. The CdS nanoparticle was uniformly dispersed on the surface of HRP, and the modification ameliorated the overgrowth, agglomeration and shortened the carrier migration distance of HRP, thereby significantly enhancing the photoreduction rate for Cr(VI). The strongest photocatalytic activity of the 1%CdS/HRP composite was obtained when the mass fraction of CdS was 1%. The reduction rate of Cr(VI) was 1.4 × 10−1 min−1, which was 17.5 times that of HRP. After five cycles of photoreduction experiments, 1%CdS/HRP still possessed high photocatalytic activity (91.7%). The lower PL intensity of 1%CdS/HRP indicated the lower recombination rate of the photoelectrons and holes. The intensity of the transient photocurrent signal was significantly higher after the compounding of CdS and HRP, indicating the increase in the number and density of photogenerated carriers. A series of experimental results showed that the construction of heterojunction between CdS and HRP contributed to the intimate interfacial contact, which was beneficial for charge separation and transfer, and improved the photocatalytic performance of the catalyst.

Growing indium antimonide single crystals with a diameter of 100 mm by the modified Chochralsky method

At present, all over the world there is a tendency to increase the diameters of single crystals of both elementary semiconductors and semiconductor compounds. There are reports indicating the use of single crystals of III-V semiconductors with a diameter of four to six inches. So far, indium antimonide single crystals up to 75 mm in diameter have been obtained in Russia.Indium antimonide is the element base of the broadest field of solid-state electronics — optoelectronics. On its basis, linear and matrix photodetectors are manufactured, operating in the spectral wavelength range of 3-5 microns, which are used as a viewing element in thermal imaging systems.In this work, we selected the thermal growth conditions and obtained indium antimonide single crystals 100 mm in diameter in the crystallographic direction [100]. The solution of this problem has made it possible to significantly increase the yield of suitable photodetectors.Single crystals 100 mm in diameter were grown by the Czochralski method in a two-stage process. The design of the graphite heating unit was enlarged and matched to a working crucible with a diameter of 150 millimeters and a load of 4.5-5 kg.The Van der Pauw method was used to measure the electrical properties of the obtained single crystals, which corresponded to the standard parameters of undoped indium antimonide. Using an optical microscope, the etching pits were counted using the 9-field method. The dislocation density in crystals with a diameter of 100 mm was ≤ 100 cm-2 and corresponded to the values ​for crystals of 50 mm.

Soft‐switching non‐isolated high step‐up three‐level boost converter using single magnetic element

Here, a soft switched three-level boost converter with high voltage gain is proposed which is suitable for high step-up applications with wide output power range. In this converter, a ZVT auxiliary circuit is used which provides soft switching in a wide range of output power independent of load variation. Utilizing coupled-inductors with one magnetic core removes extra auxiliary core in the soft switching circuit and provides high voltage gain in conjunction with size reduction. Also, the secondary and tertiary leakage inductances of the coupled-inductors minimize the reverse recovery problem of the output diodes. Due to its three-level structure, it has very low voltage stress over semiconductor elements in comparison to the existing interleaved structures, resulting in using MOSFETs with low on-resistance and thus lower conduction losses and cost. Operating modes as well as analytical analysis of the proposed converter are discussed. Finally, in order to validate the proposed converter performance, experimental results from a 200-W laboratory prototype are presented.

INCREASING THE EFFICIENCY OF SOLAR ELECTRICAL PANELS BY CONVERTING THEM INTO HYBRIDS

Non-traditional energy has recently been more and more integrated into the modern energy system of Ukraine. The geographical location opens up great opportunities for the development of manyrenewable energy sources, including solar energy. In particular, Ukraine has already built some of the world's largest solar photovoltaic plants. However, their use is largely effective due to government subsidies in the form of a "green tariff" and other measures taken by the country's government. If these subsidies are reduced or eliminated, the use and construction of new such plants may be on the verge of recoupment. One of the main ways to increase their competitiveness is to increase the efficiency of using existing stations and introduce a universal low-cost solution for projected solar stations. The increase in the efficiency of solar photovoltaic modules is limited not only by design features, but also by the features of their application. At maximum illumination during the year, the most intense heating of these panels occurs. According to the technical characteristics of individual panels, the decrease in their effectiveness depends on their temperature coefficient. Direct cooling of the panels is an effective way to reduce the effect of this temperature coefficient. To improve these photovoltaic panels, it is proposed to turn them into a hybrid collector. To do this, a special transparent screen with a coolant circulating inside is fixed on the surface of the solar panel. The external arrangement of the screen offers a number of significant advantages over existing commercial hybrid collector models. Cooling the panel with this screen can result in a relatively large increase in power generation due to the intense cooling of the surface and the semiconductor elements themselves.