Elemental Semiconductors Research Articles

Laser Thermal Processing of Group IV Semiconductors for Integrated Photonic Systems

In the quest to expand the functionality and capacity of group IV semiconductor photonic systems, new materials and production methods are constantly being explored. In particular, flexible fabrication and postprocessing approaches that are compatible with different materials and allow for tuning of the components and systems are of great interest. Within this research area, laser thermal processing has emerged as an indispensable tool that can be applied to enhance and/or modify the material, structural, electrical and optical properties of group IV elemental and compound semiconductors at various stages of the production process. Herein, the recent progress made in the application of laser processing techniques to develop integrated semiconductor systems in both fiber‐ and planar‐based platforms is evaluated. Laser processing has allowed for the production of semiconductor waveguides with high crystallinity in the core and low optical losses, as well as postfabrication trimming of device characteristics and direct writing of tunable strain and composition profiles for bandgap engineering and optical waveguiding. For each platform, the current challenges and opportunities for the future development of laser‐processed integrated semiconductor photonic systems are presented.

Nanoscale dynamics during self-organized ion beam patterning of Si. II. Kr+ bombardment

Despite extensive study, fundamental understanding of self-organized patterning by broad-beam ion bombardment is still incomplete and controversial. Understanding the nanopatterning of elemental semiconductors, particularly silicon, is both foundational for the broader field and of intrinsic scientific and technological interest itself. This is the second component of a two-part investigation of the kinetics and fluctuation dynamics of self-organized nanoscale ripple development on silicon during 1 keV Ar$^+$ (Part I) and Kr$^+$ bombardment. Here, it's found that the ion-enhanced viscous flow relaxation is essentially equal for Kr$^+$-induced patterning as previously found for Ar$^+$ patterning. The magnitude of the surface curvature dependent roughening rate in the early stage kinetics is larger for Kr$^+$ than for Ar$^+$, qualitatively consistent with expectations for erosive and mass redistributive contributions to the initial surface instability. As with the Ar$^+$ case, fluctuation dynamics in the late stage show a peak in correlation time at the length scale corresponding to the dominant structural feature on the surface -- the ripples. Analogy is made to the phenomenon of de Gennes narrowing in liquids, but significant differences are also pointed out. Finally, it's shown that speckle motion during the surface evolution can be analyzed to determine spatial inhomogeneities in erosion rate and ripple velocity on the surface. This allows the direction and speed of ripple motion to be measured in real time, a unique capability for measuring these fundamental parameters outside the specialized environment of FIB/SEM systems.

Identification of Point Defects in Atomically Thin Transition-Metal Dichalcogenide Semiconductors as Active Dopants.

Selective doping in semiconductors is essential not only for monolithic integrated circuity fabrications but also for tailoring their properties including electronic, optical, and catalytic activities. Such active dopants are essentially point defects in the host lattice. In atomically thin two-dimensional (2D) transition-metal dichalcogenides (TMDCs), the roles of such point defects are particularly critical in addition to their large surface-to-volume ratio, because their bond dissociation energy is relatively weaker, compared to elemental semiconductors. In this Mini Review, we review recent advances in the identifications of diverse point defects in 2D TMDC semiconductors, as active dopants, toward the tunable doping processes, along with the doping methods and mechanisms in literature. In particular, we discuss key issues in identifying such dopants both at the atomic scales and the device scales with selective examples. Fundamental understanding of these point defects can hold promise for tunability doping of atomically thin 2D semiconductor platforms.

Machine learning classification of binary semiconductor heterostructures

Heterostructures of two semiconductors are at the heart of semiconductor devices with tremendous technological importance. The prediction and designing of semiconductor heterostructures of a specific type is a difficult materials science problem, posing a challenge to experimental and computational investigations. In this study, we first establish that the prediction of heterostructure type can be made with good accuracy from the knowledge of the band structure of constituent semiconductors. Following this, we apply machine learning, built on features characterizing constituent semiconductors, on a known dataset of binary semiconductor heterostructures extended by a synthetic minority oversampling technique. A significant feature of engineering made it possible to train a classifier model predicting the heterostructure type with an accuracy of $89%$. Using the trained model, a large number (872 number) of unknown heterostructure semiconductor types involving elemental and binary semiconductors is theoretically predicted. Interestingly, the developed scheme is found to be extendable to heterojunctions of semiconductor quantum dots.

Optimization of a microchannel heat sink using entropy minimization and genetic aggregation algorithm

A copper heat sink with rectangular U-shaped microchannels for cooling high power laser diode arrays was numerically optimised. The control volume method based commercial software was applied for solving heat transfer and fluid flow in the considered device. The optimisation procedure included over 130 various geometrical configurations with five independent geometric parameters. The Entropy Generation Minimization criterion was applied to find the optimal geometric structure. Some relations between geometrical parameters of the microchannel heat sink were analysed through statistical studies and two most important ones, i.e., the relative height (α) and width (β) of a single microchannel, were selected. Using the genetic aggregation, the entropy generation characteristics were determined as a function of α and β as well as mass flow rate of cooling medium (Ġ). The most optimal from the second law of thermodynamics point of view configuration was the one with αopt = 0.86, βopt = 0.347 and Ġ = 0.00183 kg/s. Comparing with the initial geometry, over 35% reduction of irreversibility losses for the optimal heat sink had been achieved, i.e., heat sink thermodynamic efficiency increases from 90.05% to 91.8%, while maximum temperature of cooled semiconductor element was reduced from 333.3 K to 324.2 K.

A bidirectional multiport DC‐DC converter applied for energy storage system with hybrid energy sources

SummaryThis paper presents a novel bidirectional multiport DC‐DC converter for the electrical vehicles with hybrid energy sources. The benefits of the suggested converter are high voltage conversion ratio and high efficiency, simple structure, low voltage stress across the semiconductor elements, low number of components, and common ground features. It has two bidirectional ports, which are suitable for energy storage systems (ESS) such as a battery. Due to the step‐up and step‐down operations of the proposed converter, it can charge and discharge the ESS. Additionally, only two power switches with low ON‐state resistance are utilized that make the control circuit to be simple. Furthermore, the suggested converter has low number of component, which leads to decrease its volume and cost. The operation principle in buck and boost mode is analyzed thoroughly. Finally, to verify the analysis and effectiveness of the proposed structure, a laboratory prototype is built with 12‐ and 20‐V input voltages and a power rating of 120 W used in 50‐kHz operating frequency.

Flexible thermoelectric generator with liquid metal interconnects and low thermal conductivity silicone filler

Harvesting body heat using thermoelectricity provides a promising path to realizing self-powered, wearable electronics that can achieve continuous, long-term, uninterrupted health monitoring. This paper reports a flexible thermoelectric generator (TEG) that provides efficient conversion of body heat to electrical energy. The device relies on a low thermal conductivity aerogel–silicone composite that secures and thermally isolates the individual semiconductor elements that are connected in series using stretchable eutectic gallium-indium (EGaIn) liquid metal interconnects. The composite consists of aerogel particulates mixed into polydimethylsiloxane (PDMS) providing as much as 50% reduction in the thermal conductivity of the silicone elastomer. Worn on the wrist, the flexible TEGs present output power density figures approaching 35 μWcm−2 at an air velocity of 1.2 ms−1, equivalent to walking speed. The results suggest that these flexible TEGs can serve as the main energy source for low-power wearable electronics.

Anatomical movement replicator applied to activities in ionizing radiation fields

The aim of this work is to demonstrate the need to develop more efficient means for radiological protection, making use of the latest automation and robotics technologies. A manipulator model has been developed that has technological differentials that can positively influence the performance and cost of remote manipulation. The built-in equipment has a Slave manipulator, developed without using semiconductor elements. They are housed in the control center, which is attached to the manipulator via umbilical cord, facilitating the equipment adaptation in hot cells and other working environments. The arrangement of the joints and the links, have similarities with the anatomy of the human arm, improving the instinctively of the operation. To demonstrate its technological feasibility, a prototype Master-Slave manipulator was designed, and built using three control programs, which were written exclusively for this work. It was also designed to reduce construction and operation costs, making it accessible to most areas. The results obtained with the prototype construction are shown to be promising, providing an incentive to continue the development of manipulators using similar technologies. The equipment, obtained satisfactory results in relation to the operability, being able to perform movement tasks of loads, as foreseen in the project.

Study of Changes in the Current–Voltage Characteristics of a Semiconductor Diode When Powerful High-Frequency Signals Pass Through It

Abstract—An experimental stand has been created to assess the characteristics of the electromagnetic field under which the current–voltage (I–V) characteristic of semiconductor elements change. The developed stand was used for a series of experiments on the effect of signals with different parameters on a KD520A diode in order to record changes in the slope of the diode’s I–V characteristic as an onset degradation feature of the p–n-junction. This is done by recording the amplitudes of higher harmonics under the action of microwave signals.

Overcoming Phase‐Purity Challenges in Complex Metal Oxide Photoelectrodes: A Case Study of CuBi2O4

AbstractThe widespread application of solar‐water‐splitting for energy conversion depends on the progress of photoelectrodes that uphold stringent criteria from photoabsorber materials. After investigating almost all possible elemental and binary semiconductors, the search must be expanded to complex materials. Yet, high structural control of these materials will become more challenging with an increasing number of elements. Complex metal‐oxides offer unique advantages as photoabsorbers. However, practical fabrication conditions when using glass‐based transparent conductive‐substrates with low thermal‐stability impedes the use of common synthesis routes of high‐quality metal‐oxide thin‐film photoelectrodes. Nevertheless, rapid thermal processing (RTP) enables heating at higher temperatures than the thermal stabilities of the substrates, circumventing this bottleneck. Reported here is an approach to overcome phase‐purity challenges in complex metal‐oxides, showing the importance of attaining a single‐phase multinary compound by exploring large growth parameter spaces, achieved by employing a combinatorial approach to study CuBi2O4, a prime candidate photoabsorber. Pure CuBi2O4 photoelectrodes are synthesized after studying the relationship between the crystal‐structures, synthesis conditions, RTP, and properties over a range of thicknesses. Single‐phase photoelectrodes exhibit higher fill‐factors, photoconversion efficiencies, longer carrier lifetimes, and increased stability than nonpure photoelectrodes. These findings show the impact of combinatorial approaches alongside radiative heating techniques toward discovering highly efficient multinary photoabsorbers.

Experimental study of neutron irradiation effect on elementary semiconductor devices using Am-Be neutron source

An experiment has been conducted to evaluate the lifetime, reliability and operational performance of elementary semiconductor devices in the neutron radiation environment which supports to reduce the fatal in measurements and plan the preventive actions in nuclear facilities. It will also support the enhancement of electronics for nuclear facilities. The elementary semiconductor devices used in the experiment are Diode (1n4007), Zener Diode (5.1v), Light Emitting Diode, Transistor (BC547, 2n3904), Voltage controlling IC (7805), Operational Amplifier (LM741) and Optocoupler (4n35). The selection of devices has been made by keeping in mind their application in transmitting devices (i.e. Temperature transmitter, pressure transmitter, flow transmitter, monitors and controllers) for Indian test blanket system in ITER. Such devices are also used in general nuclear electronics. The devices have been irradiated in the Am-Be neutron source environment. The maximum fluence has been given up to 1011 n/cm2. The neutron source has energy range from low to high. All semiconductor devices have been characterized before and after irradiations. The deviation of 5 - 10% is observed in diodes I-V characteristics whereas transistors show a bit higher deflection in basic functionality. Optocoupler shows more than 50% deviation in its basic characteristics whereas voltage-controlling IC is not even functioning after the irradiation of 1011 n/cm2. The paper describes the details of the experiment and the behavior of semiconductor devices after irradiation. The experiment supports the selection and further research of the Indian test blanket system instruments.

ДОСЛІДЖЕННЯ ФАЗОВОЇ РІВНОВАГИ СПОЛУК ЦИНК-ТЕЛУР ДЛЯ УДОСКОНАЛЕННЯ ВЛАСТИВОСТЕЙ ФУНКЦІОНАЛЬНОГО МАТЕРІАЛУ РАДІАЦІЙНИХ СЕНСОРІВ

The phase equilibrium studies of ZnTe compounds are studied in order to improve the properties of one of the main functional materials of radiation sensors. To control the properties of GdZnTe compounds as the most promising materials for radiation diagnostics, it is necessary to ensure the quality and control of the parameters of the compounds from which it is technologically made. A comparative evaluation of the possibilities of using the considered binary compounds to create semiconductor sensors shows their advantages in comparison with elementary semiconductors. Among binary compounds, GdTe has undoubted advantages. However, this material cannot solve all the problems and eliminate the known shortcomings of existing semiconductor sensors. Such capabilities have solid solutions of broadband compounds, among them the most promising GdTe - ZnTe, forming wideband solid solutions of Gd x Zn 1-xTe (CCT or CZT). Technologically determined areas of temperature and partial pressure of zinc over ZnTe systems. Processional changes of lattice parameters in ZnTe alloys. Precise measurements of the lattice parameter in ZnTe alloys saturated with Zn and Te, respectively, showed that the lattice constant of alloys equal to 6.1026 ± 0.0001 Å practically does not change. The region of homogeneity, according to experimental data on vapor pressure should not exceed 0.2 at.%.

Gate-controlled ambipolar transport in b-AsP crystals and their VIS-NIF photodetection.

As a new two-dimensional elemental layered semiconductor, black phosphorus (b-P) has received tremendous attention due to its excellent physical and chemical properties and has potential applications in the fields of catalysis, energy, and micro/nano-optoelectronic devices. However, studies have found that b-P is very unstable and will decompose within a few minutes under humid air conditions. Element doping is an effective method for adjusting the physical and chemical properties of crystals. Theoretical and experimental studies have confirmed that the stability of b-P crystals is significantly improved after arsenic doping, and the crystals also exhibit excellent photoresponse and electrical transport performances. In this work, we investigate the physical properties of a component of black arsenic phosphorus crystals (b-As0.084P0.916) and the potential applications in field effect transistors (FETs) and broadband photodetectors. An obvious ambipolar behavior is observed in the transfer characteristics of b-As0.084P0.916 based FETs, with drain current modulation on the order of 105 and the highest charge-carrier mobility of up to 147 cm2 V-1 s-1. The physisorption of atmospheric species on the surface of the FETs is the main factor for the formation of Schottky contacts between the Au electrodes and the b-As0.084P0.916 crystal. Temperature-dependent electrical characteristics show that the Fermi level shifts from the valence band to the middle level between the conduction band and valence band as the temperature decreases. In addition, the FETs also exhibit excellent photoresponse properties from the visible to near-infrared region (450-2200 nm), with a responsivity of 37 A W-1, a specific detectivity of 7.18 × 1010 Jones, and a fast response speed (τrise ≈ 0.04 s and τdecay ≈ 0.14 s). These results suggest that b-As0.084P0.916 crystals are a promising candidate for future electronic and optoelectronic devices.

Soft Body Belt-Type Touch Sensor With Impact Resistance: A Study of Dynamic Behavior

We report the development of a novel soft body touch sensor capable of measuring contact force along its length. The sensor can be embedded in soft objects and on curved surfaces for smart furniture, interactive electronics, and general robotics applications. The sensor uses pneumatic transduction principle and achieves both high sensitivity and impact loading tolerance. The development is motivated by the needs of consumer electronics industries for smart furniture and interactive toys. The current work fills a gap of existing soft-bodied touch sensors. The main sensor body is completely polymeric and contains no conductive or semiconducting material elements. It exhibits high pass frequency response to reject common mode contact forces or shape variations. The central question addressed by this paper is dynamic behavior of this sensor under normal and impact touch force. In this study we developed a theoretical model for the sensor output and validated with experimental measurements. We modeled sensor behavior under two operational regimes of different unloading speed. Depending on the rate of change, the sensor could be in force limited relaxation mode or elastic relaxation (free relaxation) mode. Measurements have been performed to capture time constants of occupant behavior in a smart cushion application.

Experimental study of a double-circuit optoelectronic generator of radio-frequency signals

An urgent issue is the development of radio frequency generators operating in the microwave range, with high frequency stability, wide tuning band, as well as small size and weight. Microwave signal generators are used as part of radio electronic devices and devices for telecommunication, radio navigation and metrological purposes; therefore, improving their main characteristics is an important goal for the further development of radio electronic devices. A technological feature of optoelectronic generators is the combined use of solid-state components of modern HF and UHF optoelectronics, fiber optics and traditional components of UHF/EHF technology. According to the principle of operation and construction scheme, the optoelectronic generator is similar to the classic radio-frequency self-oscillator with a delay line in the feedback circuit. A feature of its work is the multifrequency nature of the generated oscillations, for which the conditions for amplitude balance and phase balance are satisfied. In the case of an optoelectronic generator, a feedback ring with a resonant system and a delay element is made using a single-mode fiber of a certain length. The signal delay time in the feedback loop is a significant parameter of the optoelectronic generator, which affects the noise and spectral characteristics of the generator. With an increase in the length of the fiber-optic path, the delay time in the feedback loop increases, thereby reducing the level of frequency noise. However, with an increase in the length of the fiber-optic path, the distance between adjacent modes of the optoelectronic oscillator also decreases, increasing the requirements for the bandwidth of the band-pass filter. The solution to this problem was the use of a multi-circuit optoelectronic generator. The paper considers a model created by the authors for a two-circuit optoelectronic generator with fiber-optic paths 1000 m and 30 m long. The available element base did not allow to reduce the generator's weight and dimensions. On this model, the characteristics of the circuit elements have been experimentally studied. The spectral characteristics of the generator have been estimated theoretically, which are in good agreement with the results of practical research. Phase noise is an important parameter in generator evaluation. Oscillators used as reference and measuring oscillators must certainly have a high frequency stability of the generated signal. Oscillations in autogenerators arise due to the effect of intrinsic noise in the circuit elements, which is one of the reasons for the occurrence of noise in the spectrum of the generator output signal. Intrinsic noise includes thermal, shot and flicker noises in semiconductor elements of generators. The article calculates the power spectral density of the phase noise of a single-loop oscillator and a dual-loop oscillator, which confirmed the assumption about a compromise between the noise level and the requirement for the filter bandwidth in a single-loop optoelectronic oscillator. An important advantage of optoelectronic generators, in comparison with generators built according to classical circuitry, is the absence of a compromise between the frequency tuning band of the device generation and the level of frequency noise.

A high efficiency soft‐switched DC–DC converter with high voltage conversion ratio

SummaryThis work proposes a kind of DC–DC topology with a higher voltage conversion ratio. The suggested converter utilizes a coupled inductor and a voltage multiplier cell to enhance the voltage conversion ratio. The voltage multiplier cell has the feature of the clamping circuit, which can decrease the maximum voltage of the semiconductors elements. In the presented structure, only one lower ON‐state resistance (RDS‐ON) power switch is utilized that makes the control circuit to be simple. The proposed converter has soft‐switching features such as zero‐current switching (ZCS) and zero voltage switching (ZVS) that lead to decrease the diodes reverse recovery losses and increase the efficiency. Besides, the ripple value of the input current is lower than the other similar works. The high efficiency and low input current ripple make the suggested converter suitable for photovoltaic (PV) applications. In order to approve the technical analysis of the recommended structure, technical investigations and comparison study with some similar structures are carried out. Finally, for demonstrating the advantages of the presented structure, a laboratory circuit is built with 12‐V DC source voltage, 120‐V load voltage, and power rate of 100 W in 50‐kHz operation frequency.

Identification of Gate Turn-off Thyristor Switching Patterns Using Acoustic Emission Sensors.

Modern seagoing ships are often equipped with converters which utilize semiconductor power electronics devices like thyristors or power transistors. Most of them are used in driving applications such as powerful main propulsion plants, auxiliary podded drives and thrusters. When it comes to main propulsion drives the power gets seriously high, thus the need for use of medium voltage power electronics devices arises. As it turns out, power electronic parts are the most susceptible to faults or failures in the whole electric drive system. These devices require efficient cooling, so manufacturers design housings in a way that best dissipates heat from the inside of the chips to the metal housing. This results in susceptibility to damage due to the heterogeneity of combined materials and the difference in temperature expansion of elements inside the power device. Currently used methods of prediction of damage and wear of semiconductor elements are limited to measurements of electrical quantities generated by devices during operation and not quite effective in case of early-stage damage to semiconductor layers. The article presents an introduction and preliminary tests of a method utilizing an acoustic emission sensor which can be used in detecting early stage damages of the gate turn-off thyristor. Theoretical considerations and chosen experimental results of initial measurements of acoustic emission signals of the medium voltage gate turn-off thyristor are presented.

Development of an experimental installation for thermoelectric cooling of the chamber

The article is devoted to the development of an experimental installation for studying the process of thermoelectric cooling based on the Peltier element when performing laboratory work and conducting scientific research. The developed installation allows not only to obtain low temperatures by applying voltage to series-connected semiconductor elements, but also to test modules with various physical and chemical properties.

Quasi-Resonant Bridgeless PFC Converter With Low Input Current THD

In this article, a quasi-resonant bridgeless power factor correction (PFC) converter is presented. Aiming to improve the input current total harmonic distortion, a single auxiliary switch with low voltage stress than the similar counterparts is employed. Due to resonant operation, the size and value of the passive components are reduced and maximum voltage gain of four is achieved which is higher than that of conventional buck PFC converter. Also, soft switching condition for the main semiconductor elements is realized from 20% of nominal power to full load and entire input voltage range (90 to 130 Vrms) without employing any extra component. The operating modes are explained and the theoretical analysis is discussed in details. A straightforward design procedure for the proposed converter is presented. A 200 W, 160 kHz laboratory prototype is implemented to verify the theoretical analysis and the effectiveness of the proposed topology.

A fast and large bandwidth superconducting variable coupler

Variable microwave-frequency couplers are highly useful components in classical communication systems and likely will play an important role in quantum communication applications. Conventional semiconductor-based microwave couplers have been used with superconducting quantum circuits, enabling, for example, the in situ measurements of multiple devices via a common readout chain. However, the semiconducting elements are lossy and furthermore dissipate energy when switched, making them unsuitable for cryogenic applications requiring rapid, repeated switching. Superconducting Josephson junction-based couplers can be designed for dissipation-free operation with fast switching and are easily integrated with superconducting quantum circuits. These enable on-chip, quantum-coherent routing of microwave photons, providing an appealing alternative to semiconductor switches. Here, we present and characterize a chip-based broadband microwave variable coupler, tunable over 4–8 GHz with over 1.5 GHz instantaneous bandwidth, based on the superconducting quantum interference device with two parallel Josephson junctions. The coupler is dissipation-free and features large on-off ratios in excess of 40 dB, and the coupling can be changed in about 10 ns. The simple design presented here can be readily integrated with superconducting qubit circuits and can be easily generalized to realize a four- or more port device.