Improvement of the optical properties of GaN epilayers on Si(111): Impact of GaAs layer thickness on Si and pre‐growth strategy

This paper reports the effect of the GaN coating layer on the optical properties of GaN epilayers grown on GaAs/Si(111). Almost crack free GaN epilayers are found to be grown when a thin (∼25 nm) GaN coating layer is inserted on 0.5 and 2 μm GaAs layers at 550 °C. Then nitridation of the GaAs layer is done through the coating layer by NH3 flow while the substrate temperature is ramped at 1000 °C for epilayer growth. An attempt has also been made by implementing an additional GaN interlayer at 800 °C while growth is continued for epilayer growth. For this growth strategy, cracks also happened without improvement of the epilayer quality. PL measurements show high excitonic peak energy and high excitonic to yellow band intensity ratio for GaN epilayers grown on the 0.5 μm GaAs converted layer (CL) using a thin GaN coating layer. Those values are also found to be comparable/ better than for epilayers grown on 2 μm CL

mcSi and CdTe solar photovoltaic challenges: Pathways to progress

Multi-crystalline Si (mcSi) and CdTe solar photovoltaic technologies have gained significant improvement. Shockley–Queisser (S-Q) limit consideration further progress of open-circuit voltage (Voc), fill factor (FF) and the efficiency of CdTe cell are anticipated. Sub-bandgap parasitic absorption, grain boundaries and back contacts recombination lessening are vital to minimize these opto-electrical losses. mcSi and CdTe heterojunction (HJ) cells’ intrinsic thermal co-efficient to optical (bandgap) loss, interface and bulk defects and related thermal diffusion are possible opto-electrical limitations. Wafer based mcSi passivated emitter rear contact (PERC) and tunnel oxide passivated contact (TOPCon) over Al back surface field (Al-BSF) contact have incredibly progressed in current decades. Similar as mcSi cell, advancement of commercial CdTe cell is desired. Reviewing CdTe and mcSi/cSi (photo-physical similarity) based one hundred and fifty research papers it is comprehended that not only band aligned but also thin, transparent passivation window and electron reflector as barrier are central to minimize the shortcomings. CdTe absorber thickness-dependent Voc and fill factor trade-off while diverse window and barrier layer performance review are realized optical transparencies to electrical loss outcome. Stated opto-electrical development purpose thin absorber supportive band and lattice matching double HJ or graded CdSexTe1-x/CdTe HJ is possible realistic pathways. mcSi thin wafer is exposed to minimize bulk degradation that is caring for a stable and cost-effective PV. Finally, CdTe solar cells present limitations to laboratory design towards the best progression trails are focused. It is anticipated to limit the levelized cost of energy (LCOE)

Optoelectronic properties of improved GaN semiconductor on Si (111) using growth approaches and different interlayer’s

The crystalline quality of wider direct band gap semiconductor (3.4 eV) h-GaN epilayer grown on Si (111) is evaluated by different growth approaches and by using different interlayer’s. The investigations of GaN epilayer crystal quality for the template of converted porous GaN layer formed by novel nitridation process of thin (2 and 0.5 μm) GaAs layer on Si (111) and on C+ ion implanted very thin SiC layer formed on Si (111) and grown ambient effect are made. Epilayer grown on thinner non-isoelectronic converted SiC templates is found to broaden its PL line width whereas epilayer grown on porously converted GaN layer fromed from iso- electronic GaAs (111) layer on Si (111) is found narrow line width. H2 ambient grown film better crystalline quality and higher PL Ex. peak energy is found as compared to N2 ambient grown film. Low temperature PL measurement, similarity between defect related donor-acceptor peaks (DAP) to defect related yellow band luminescence at the room temperature PL measurement is also found. Grown epilayer different characterization reveals better crystalline quality h-GaN is achieved by using thin isoelectronic GaAS interlayer on Si (111) with H2 grown ambient

Novel magnetic core materials impact modelling and analysis for minimization of RF heating loss

The eddy current that exists in RF transformer/inductor leads to generation of noise/heat in the circuit and ultimately reduces efficiency in RF system. Eddy current is generated in the magnetic core of the inductor/transformer largely determine the power loss for power transferring process. The losses for high-frequency magnetic components are complicated due to both the eddy current variation in magnetic core and copper windings reactance variation with frequency. Core materials permeability and permittivity are also related to variation of such losses those linked to the operating frequency. This paper will discuss mainly the selection of novel magnetic core materials for minimization of eddy power loss by using the approach of empirical equation and impedance plane simulation software TEDDY V1.2. By varying the operating frequency from 100 kHz to 1GHz and magnetic flux density from 0 to 2 Tesla, the eddy power loss is evaluated in our study. The Nano crystalline core material is found to be the best core material due to its low eddy power loss at low conductivity for optimum band of frequency application

A review on global emissions by e-products based waste: Technical management for reduced effects and achieving sustainable development goals

In the 21st century, a great amount of electrical and electronic waste (e-waste) has accumulated, and the unregulated nature of its disposal and recycling represents a particular hazard in a global context. For the purposes of e-waste management, there must be more emphasis on the scientific processes for recycling, reusing and remanufacturing precious materials. Resource management is related to energy management; therefore, the harvesting of costly materials from e-waste is important for both energy management and sustainable development. At present, a lack of scientific recycling of a significant amount of e-waste is a source of environmental pollution and health hazards that are having a detrimental effect on sustainable development goals. It is necessary to find a process for recovering valuable materials from e-waste with the minimum possible environmental impact. At present, it is essential to modify the process of electrical and electronic products (e-products) becoming e-waste, and the subsequent process of e-waste recycling, in order to lessen the impact in terms of pollution. E-waste scientific recycling initiatives can reduce the environmental impact of the process, which in turn can support a shift from the current linear flow of costly materials to a more sustainable circular flow. Furthermore, internal consumption loss, emissions, and heating loss from e-products are the main factors contributing to the loss of energy efficiency in the process, which in turn contributes to environmental pollution. Promoting green innovation in the manufacturing process of e-products, as well as their reuse, can reduce the environmental impact of e-waste in near future. Both of these pathways are imperative for a less polluted, low-toxic environment and sustainable development. However, the sustainable development initiative of the United Nations Environmental Programme (UNEP) policy framework is the ultimate goal. This is expected to support the management of environmental pollution, maintaining it at an acceptable level, while also preventing hazardous risks to human health. Hence, this review examines the prospects for achievable environmental sustainability through technological developments

An effective simulation analysis of transient electromagnetic multiple faults

Embedded encryption devices and smart sensors are vulnerable to physical attacks. Due to the continuous shrinking of chip size, laser injection, particle radiation and electromagnetic transient injection are possible methods that introduce transient multiple faults. In the fault analysis stage, the adversary is unclear about the actual number of faults injected. Typically, the single-nibble fault analysis encounters difficulties. Therefore, in this paper, we propose novel ciphertext-only impossible differentials that can analyze the number of random faults to six nibbles. We use the impossible differentials to exclude the secret key that definitely does not exist, and then gradually obtain the unique secret key through inverse difference equations. Using software simulation, we conducted 32,000 random multiple fault attacks on Midori. The experiments were carried out to verify the theoretical model of multiple fault attacks. We obtain the relationship between fault injection and information content. To reduce the number of fault attacks, we further optimized the fault attack method. The secret key can be obtained at least 11 times. The proposed ciphertext-only impossible differential analysis provides an effective method for random multiple faults analysis, which would be helpful for improving the security of block ciphers

Formation of air-gap structure at a GaN epilayer/substrate interface by using an InN interlayer

We propose a new technique for “air‐gap” formation at a GaN/sapphire interface by using an InN interlayer. This is aimed to grow epitaxial GaN films with reduced stress and cracks. First, an InN interlayer of about 0.2 μm thick is grown at 600 °C in atmospheric pressure. Then a 30 nm‐thick GaN buffer layer is grown on the InN layer at 550 °C. The substrate temperature is ramped up to 1000 °C in the NH3 flow, and finally a 1.5 μm‐thick GaN epilayer is grown on the annealed GaN buffer layer using nitrogen carrier gas. Consequently, an “air‐gap” structure is naturally formed close to the substrate surface. During the ramping period of substrate temperature, the InN layer decomposes due to its thermal instability and metallic In is formed. It is found that metallic In drops as a result of InN decomposition contribute to the air‐gap formation. No cracks are found on the GaN surface and a reduced stress in the layer is confirmed by PL and Raman shift measurements

Development of a license plate recognition system for a non-ideal environment

A new algorithm for license plate character recognition system is proposed on the basis of Signature analysis properties and features extraction. Signature analysis has been used to locate license plate region and its properties can be further utilised in supporting and affirming the license plate character recognition. This paper presents the implementation of Signature Analysis combined with Features Extraction to form feature vector for each character with a length of 56. Implementation of these two methods is used in tracking of vehicle’s automatic license plate recognition system (ALPR). The developed ALPR comprises of three phase. The recognition stage utilised the vector to be trained in a simple multi-layer feed-forward back-propagation Neural Network with 56 inputs and 34 neurons in its output layer. The network is trained with both ideal and noisy characters. The results obtained show that the proposed system is capable to recognise both ideal and non-ideal license plate characters. The system also capable to tackle the common character misclassification problems due to similarity in characters

Electrospinning Growth Parameters Dependent PVP: PC71BM Nanofiber Structure Characterizations and Modeling

As green materials, the organic nano-fiber membranes are very potential for diverse functional purposes. The growth parameters based fiber alignment; surface morphology and diameter are key attentions to control mechanical, structural, electrical, and optical properties. These physical aspects of nanofiber are diversified its practical significance in which control of growth techniques is vital. Electrospinning is a facile but pragmatic approach to adjust the growth process by regulating growth parameters. In this study, fabrication of spinning parameter preference to control the nanofiber shape, diameters, and crystalline property are investigated. Different % weight of PVP and PC71BM mixture solution for electrospinning are used in this study. It is observed that the average applied field and solution concentration of active materials are paramount to well-aligned uniform diameter nanofiber having better structure and crystalline properties. The scanning electron microscopic (SEM) study of nanofiber micrograph shows the diameter size of nanofiber and it is validated by Response Surface Model (RSM). A sharp peak of polymer fiber is shown by X-ray diffraction (XRD) that realizes worthy nano-crystalline property. The overall growth process is reinforced by validation from RSM analysis

Composition Dependence Structural and Optical Properties of Silicon Germanium (SiχGe1−χ) Thin Films

This study investigates the structural and optical characteristics of Silicon Germanium (SiGe) thin films with varying compositions and annealing temperatures for potential use in electronic and optoelectronic devices. Si0.8Ge0.2 and Si0.9Ge0.1 films were deposited onto a high-temperature quartz substrate and annealed at 600 °C, 700 °C, and 800 °C before being evaluated using an X-Ray Diffractometer (XRD), Atomic Force Microscopy (AFM), and a UV-Vis Spectrometer for structural and optical properties. The results show that increasing the annealing temperature results in an increase in crystalline size for both compositions. The transmittance for Si0.8Ge0.2 decreases slightly with increasing temperature, while Si0.9Ge0.1 remains constant. The optical band gap for Si0.9Ge0.1 thin film is 5.43 eV at 800 °C, while Si0.8Ge0.2 thin film is 5.6 eV at the same annealing temperature. XRD data and surface analysis reveal significant differences between the band edges of SiGe nano-structure materials and bulk crystals. However, the possibility of a SiGe nano-crystal large band gap requires further investigation based on our study and related research works