bluuebunny/crossref_metadata_2025 huggingface dataset:
Deep Learning Techniques for Biomedical Image Analysis in Healthcare
Authors: A. Sivakami , K. S. Balamurugan , Shanmugam Bagyalakshmi , Pitchaimuthu Sudhagar
Published: July 2020

Biomedical image analysis is very relevant to public health and welfare. Deep learning is quickly growing and has shown enhanced performance in medical applications. It has also been widely extended in academia and industry. The utilization of various deep learning methods on medical imaging endeavours to create systems that can help in the identification of disease and the automation of interpreting biomedical images to help treatment planning. New advancements in machine learning are primarily about deep learning employed for identifying, classifying, and quantifying patterns in images in the medical field. Deep learning, a more precise convolutional neural network has given excellent performance over machine learning in solving visual problems. This chapter summarizes a review of different deep learning techniques used and how they are applied in medical image interpretation and future directions.
Women's Agency and Sustainability
Authors: Yanikkaya Aydemır Pervin
Published: July 2020

The critical multitasking role that women play in agriculture, production, and ecological sustainability and their contribution as possessors of knowledge and skills have been almost ignored by the institutionalized patriarchy, such that women constituting almost half of the world's population have lacked equitable participation in decision-making, responsibilities, and benefits of development. In this chapter, the author discusses women's agency and sustainability, focusing on the activist work of two remarkable women from different socio-economic backgrounds in Turkey with whom she conducted in-depth interviews during fieldwork in İspir, Erzurum in 2012. Both women provide examples of how they have responded to issues relating to the upsurge of hydropower projects in Turkey. Although it has been almost eight years since she was in the field, she finds their perspectives and experiences relevant and important for representation of female voices and women's agency in terms of management and sustainability of water resources, particularly given the current climate crisis.
Environmental Fluoride
Authors: Malik Junaid Ahmad
Published: July 2020

Noteworthy multi-disciplinary undertakings have been taken to investigate the effects of natural fluoride ion (F) contamination since the preceding century. Fluoride is a hazard to the earth and human prosperity. Developed and developing countries are standing up to such enormous extents of issues in light of fluoride in the drinking water. Human use to fluoride has bourgeoned since World War II, on account of fluoridated water and toothpaste just as to the normal defilement by huge ventures, from aluminium to pesticides, where fluoride is an essential mechanical concoction similarly as a waste product. The chapter deals with the proportion of fluoride in nature and its impact on human prosperity, generally on the brain, endocrine system, thyroid, pineal gland, immune system, reproductive system, and organ systems. High assemblies of F in soil may really bargain the life of plants, obliterate soil microbial development, upset the soil environment, and cause soil and water defilement. This chapter further emphasizes various biological approaches for the remediation.
Cadmium- and Lead-Tolerant PGPRs as Proficient Toxicity Alleviators for Agricultural Crops
Authors: Pal Amit Kumar , Hazra Anjan , Sengupta Chandan
Published: July 2020

Agricultural lands are being polluted with different contaminants due to various anthropogenic activities like toxic discharge from Ni-Cd battery industry, tannery industry, alloying of metals like steel, application of agrochemicals, etc. Cadmium and lead contamination in agricultural land are directed towards global food insecurity. Bioremediation, stress alleviation, and phytostimulation by Cd and Pb tolerant PGPR is a promising eco-friendly method to develop sustainable agricultural system. At present, cadmium and lead-tolerant plant growth promoting rhizobacteria (PGPR) can be a sustainable option for heavy metal-contaminated agricultural lands. PGPRs such as Bacillus, Bradyrhizobium, Enterobacter, Klebsiella, Micrococcus, Pseudomonas, Ralstonia, etc. can survive the metal stress and stimulate the plant growth under Cd and Pb contaminated condition by direct or indirect plant growth promoting ability. So, these PGPRs could be exploited as biofertilizers and bioremediators under Cd or Pb stressed conditions for futuristic agricultural development.
An Eco-Friendly Approach for the Eradication of Heavy Metal Contaminants by Nano-Bioremediation
Authors: Mohanty Chandana , Satpathy Sneha Shriparna , Mohanty Sweta
Published: July 2020

Nanomaterials manifest distinct physical and chemical properties and have received much attention from researchers in different areas of environmental sciences, specifically in bioremediation. However, bioremediation may not always impart contrivable approaches when subjected to high concentrations of contaminants that are harmful to most microorganisms, which include heavy metals and salts. Nanotechnology on the other hand exhibits a number of potential environmental benefits such as treatment and remediation, pollution prevention, and sensing and detection of pollutants. Nanomaterials used towards bioremediation provide less-toxic effects on indigenous microorganisms and improve microbial biodegradation activity. Credibility of nanotechnology to cut down pollution is in its developing stage and could potentially revolutionize the field of environmental sustainability. Nano-bioremediation is a new emerging technique for remediation of pollutants using biosynthetic nanoparticles.
Recent Advancements in Bioremediation of Metal Contaminants
Authors: Ragunathan Yuvarajan , Nallakumar Kannan , Rathinavel Thirumalaisamy , Govarthanan Muthusamy , Thangaswamy Selvankumar
Published: July 2020

Biofilms are an accumulation of single or various populations of microorganisms that are present on the surfaces through membrane-bound substances due to the gene expression, which differs from free-floating expression and leads to expressed genes regulating biofilm formation and development. In this regard, recent advances in microbial-based heavy metals have propelled bioremediation as a prospective alternative to conventional techniques. Adsorption and biodegradation of organic contaminants and the immobilization, mobilization, and/or transformation of metals are the main remediation processes that can be mediated by the action of several microorganisms surviving in hostile environments with high concentrations of pollutants. The chapter discussed the formation and regulation of biofilms to degrade the metal contaminant, the importance of gene transfer, and applications of biofilm-mediated bioremediation processes.
Designing the Architecture of a Blockchain Platform
Authors: Ibáñez Javier W. , Moccia Salvatore
Published: July 2020

The financial services industry is experiencing—or better said, is suffering—an enormous paradigm shift. New technologies, combined with new consumers, are redefining the way financial institutions design products and deliver services. Furthermore, Mastercard has filed four blockchain patents to improve settlement systems. The Alastria case, explored in this paper, is a still rare phenomenon of national blockchain as a country territorial and jurisdictional case of public permissioned blockchain oriented to combine the satisfaction of public and private interests with full legal compliance.
Rule-Based Actionable Intelligence for Disaster Situation Management
Authors: Jain Sarika , Sharma Sumit , Natterbrede Jorrit Milan , Hamada Mohamed
Published: July 2020

Managing natural disasters is a social responsibility as they might cause a gloomy impact on human life. Efficient and timely alert systems for public and actionable recommendations for decision makers may well decrease the number of casualties. Web semantics strengthen the description of web resources for exploiting them better and making them more meaningful for both human and machine. In this work, the authors propose a semantic rule-based approach for disaster situation management (DSM) to reach the next level of decision-making power and its architecture for providing actionable intelligence in the domain of the earthquake. The system itself is based on a data pre-processing layer, a computation layer, and the middle layer relies on an extensive rule base of experts' advice stored over time and a disaster ontology along with its inherent semantics. The rule-based reasoning approach uses this knowledge base in combination with the expert rule base, written in SWRL rules, to infer recommendations for the response to an earthquake.
The Impact of Communication Language on Entrepreneurship in Cameroon
Authors: Tagne Joël Stephan
Published: July 2020

The objective of this study was to analyze the effects of linguistic diversity on entrepreneurship in Cameroon. More specifically, it was a question of analysing the effects of linguistic diversity first on entrepreneurial intention, then on business creation, and finally on the sustainability of the businesses created. To achieve these objectives, the authors used data from a survey of 504 individuals in the cities of Douala and Yaoundé conducted by the Laboratory of Research in Fundamental and Applied Economics (LAREFA) of the University of Dschang and using the binary probit, recursive bivariate probit, and tobit models; it was found that 1) bilingual individuals have a lower entrepreneurial intention than their monolingual counterparts; however, the fact that the individual masters several languages facilitates the transition from intention to action; 2) if linguistic diversity is varied from zero to low or medium level, then the duration of the enterprise will increase by 25 months.
Enhancing Public Engagement for Green Diwali
Authors: Kumar Vinod , Vandana  , Goyal Praveen , Kumar Divesh
Published: July 2020

The purpose of this article is to engage student community to celebrate Green Diwali. The present study makes use of various engaging activities to generate awareness about the celebrating Diwali in unsustainable manner. The effectiveness of the activities was also measured through a questionnaire-based survey. The article provides an excellent example of educating and promoting sustainable development through celebration of Green Diwali. This study will encourage other institutions in the country to promoting sustainable development activities and take the initiatives like that of Green Diwali.
New Hybrid Proposed Solution for Video Steganography Based on Clustering Algorithm
Authors: Fatnassi Ahlem , Gharsellaoui Hamza , Bouamama Sadok
Published: July 2020

Through the advent of digital information, information security has taken on a vital role. Use of the internet freely for contact has increased the attacks on users. Data protection is the present problem relating to privacy and security during storage and communication. This paper deals with a multilayered protected channel's proposal to transfer confidential data/video through a channel. The hidden video is initially encrypted using the algorithm NOLSB. The created cipher video is hidden in a larger sized video file. In addition, this video file is encrypted using the (m, k) firm technique to optimize resource efficiency and bandwidth optimization. Video shares are then sent through all the network's channels to ensure security. This approach ensures that video files could be retrieved at the end receiver even though any shares were lost over the network, without the sender needing to resend the video file.
A Review on Identity and Access Management Server (KeyCloak)
Authors: Divyabharathi D. N.  , Cholli Nagaraj G.
Published: July 2020

KeyCloak is an open source identity and access management arrangement focused on present day applications and administrations. It makes it simple to protect applications and administrations with next to zero code. The identity and access management server component provides centralized user management, authentication, and single sign-on identity brokering user federation, social login, client adapters, an admin console, and an account management console for the applications. With KeyCloak, the user management and authentication functions may be integrated with an externally managed system, such as LDAP or active directory. KeyCloak provides single sign-on infrastructure for authentication and session management. In this paper, the authors present an overview of KeyCloak that gives the objectives and features of KeyCloak and comparisons between the servers. They also present protocols of KeyCloak. Finally, benefits of KeyCloak are defined.
Age-Friendly Standards Around ICT
Authors: Waights Verina , Holland Caroline , Huchet Estelle , Fisk Malcolm
Published: July 2020

As the European population ages, there is an escalating need for age-friendly standards to support development of effective products and services involving information and communication technologies (ICT), thereby improving usability for all consumers, including older people. Co-production with users through inclusive and participatory processes provides several benefits to standardization, including enhanced understanding of market needs, clearer identification and mitigation of risks, and increased legitimacy of the standards developed. Ideally, co-production includes users from a range of backgrounds. However, older people, especially those aged over 80 years, are often the least likely in the population to be involved. This paper reports on barriers and challenges to inclusive co-production from the perspectives of a range of stakeholders participating in the European Commission-funded project PROGRESSIVE: Progressive Standards around ICT for Active and Healthy Ageing. It identifies potential ways to improve the participation of older people in the co-production of standards.
Handling Minority Class Problem in Threats Detection Based on Heterogeneous Ensemble Learning Approach
Authors: Eke Hope , Petrovski Andrei , Ahriz Hatem
Published: July 2020

Multiclass problems, such as detecting multi-steps behaviour of advanced persistent threats (APTs), have been a major global challenge due to their capability to navigates around defenses and to evade detection for a prolonged period. Targeted APT attacks present an increasing concern for both cyber security and business continuity. Detecting the rare attack is a classification problem with data imbalance. This paper explores the applications of data resampling techniques together with heterogeneous ensemble approach for dealing with data imbalance caused by unevenly distributed data elements among classes with the focus on capturing the rare attack. It has been shown that the suggested algorithms provide not only detection capability but can also classify malicious data traffic corresponding to rare APT attacks.
High-Temperature Reliability Analysis of 1200V/100A 4H-SiC Junction Barrier Schottky Diodes
Authors: Tang Yi Dan , Liu Xin Yu , Li Chengzhan , Bai Yun , Chen Hong , Yang Cheng Yue
Published: July 2020

The high-temperature (up to 200 °C) reliability analysis of 1200V/100A 4H-SiC JBS under 168 hours of high-temperature storage stress (HTSS), high-temperature reverse bias (HTRB) and high-humidity HTRB (H3TRB) stress test are reported. Results show that, all the statistical distribution of the data consistency is more dispersed after HTSS, HTRB and H3TRB test, which suggests that there are more degradation in the forward voltage and leakage current characteristics of JBS device under high temperature (up to 423K) stress. The increased reverse leakage currents after HTSS and HTRB stresses at different test temperatures are mainly due to the thermionic emission with the image force barrier height lowering. However, it is not the same phenomenon after HTRB stress. And the stability of VR under HTRB test is better than the one under HTSS test, which may be due to the migration and accumulation of charge during exposure to HTRB.
Impact of Channel Implantation on a 4H-SiC CMOS Operational Amplifier for High Temperature Applications
Authors: Albrecht Matthaeus , Pérez David , Martens R. Christian , Bauer Anton J. , Erlbacher Tobias
Published: July 2020

In this work, the impact of channel implantations (IMP) on the electrical characteristics of SiC n-and p-MOSFETs and analog SiC-CMOS operational amplifiers (OpAmp) is investigated. For this purpose, MOSFETs and Miller OpAmps with and without IMP were fabricated and electrically characterized from room temperature up to 350°C. For devices with IMP the absolute values of the threshold voltages of n-and p-MOSFETs were reduced by 1.5 V and the mobility of the n-MOSFET was increased from 13 to 23 cm2/Vs whereas the mobility of the p-MOSFET remained constant at 6 cm2/Vs. For the resulting OpAmp with IMP, the common-mode input voltage range as well as the open loop gain was increased by 1.5 V and 4 dB compared to non-implanted devices. This improvement was observed across the entire analyzed temperature range from room temperature up to 350°C.
Evaluation of Surge Reduction Performance of a SiC Avalanche Diode with Mesa Structure in a Switching Power Supply
Authors: Koseki Kunio , Yamamoto Masayuki , Tanaka Yasunori
Published: July 2020

A p-n junction diode with mesa structure by silicon carbide (SiC) has been developed to utilize the avalanche breakdown in an excessed reverse bias condition to clamp the surge voltage in switch-mode power supplies. Static voltage-current correlation by pulsed reverse voltage has been measured. The increase of the breakdown voltage was measured to be 32 volts with increased current density up to 3900 A/cm2. The operational performance in suppressing the surge voltage in a step-down DC/DC converter has been evaluated. A superior performance in suppressing the surge voltage by the SiC p-n junction diode has been confirmed. It was also found that a resonant oscillation induced during clamping period limits the performance. By a circuit analysis with an equivalent circuit model, it was found that a parasitic wiring inductance between the diode and switching element induces the resonance. It was also found that a promising way to mitigate the disturbing effect is to minimize the inductance.
Prospects of Bulk Growth of 3C-SiC Using Sublimation Growth
Authors: Wellmann Peter J. , Schuh Philipp , Kollmuss Manuel , Schöler Michael , Steiner Johannes , Zielinski Marcin , Mauceri Marco , La Via Francesco
Published: July 2020

Free standing 3C-SiC wafers with a dimeter of 50 mm and a thickness of ca. 0.8 mm have been grown on a regular base using 3C-SiC CVD seed transfer from Si wafers to a poly-SiC-carrier and a sublimation epitaxy configuration. Up to the thickness of almost 1 mm, stable growth conditions of the cubic polytype have been achieved. The high supersaturation was kept stable by the proper design of the hot zone that enables a high axial temperature gradient at the growth interface. The Sirich gas phase was realized by the application of a Tantalum getter that was integrated into the graphitebased growth cell. Furthermore, an adaption of the growth setup allowed the growth of 3C material with a diameter of 95 mm and bulk material up to 3 mm on 25 mm diameter. Computer simulations were used to determine the supersaturation of the growth setup for different source-to-seed distances. The minimum supersaturation necessary for stable growth of cubic SiC was found to be higher 0.1 for seed already containing the required 3C polytype.
Inrush Current Effects on SiC-MOSFETs for LLC Converter
Authors: Takaku Yoshimasa , Tanaka Hikaru , Takada Yosei , Nakata Shuhei
Published: July 2020

We prototyped an LLC converter using SiC-MOSFET and GaN-FET to study the device dependence of the resonant type converter characteristics and high current effects on the devices during the start-up mode.Under steady state operation, no observable difference exists between the SiC-MOSFET and GaN-FET in current and voltage waveforms and energy conversion efficiency is over 96% regardless of the device used.However, significant differences exist during the start-up mode. As for the SiC-MOSFET, the inrush current is at maximum in the first few cycles and gradually decreases to steady state. As for the effects on the device, there are no characteristic changes or current waveform fluctuation during the start-up period even after 50 repetitions.Alternately, in the case of GaN-FET, the maximum inrush current is at the first cycle and decreases rapidly to half only a few cycles later. The multi-pulse experiment shows that a single high current pulse degrades the I-V characteristics of the device and the subsequent pulse current decreases. It is also noted that the degradation could be overcome by a longer interval after the high current, however, no further improvement is seen above a 20 µs interval.
3C-SiC Bulk Growth: Effect of Growth Rate and Doping on Defects and Stress
Authors: La Via Francesco , Mauceri Marco , Scuderi Viviana , Calabretta Cristiano , Zimbone Massimo , Anzalone Ruggero
Published: July 2020

We report the study of the effect of the growth rate and of the doping on the stress and the defect density of a Cubic Silicon Carbide (3C-SiC) bulk layer grown at low temperature on a silicon substrate. After the growth process, the silicon substrate was melt inside the CVD reactor used for the deposition and then the intrinsic stress was measured by the curvature of the wafer without influence of the thermal stress between silicon and 3C-SiC. A considerable increase of the curvature was observed increasing the doping of the layer. The average stress is compressive and then produces a convex bow. At the same time, the average quality of the grown material deteriorates increasing the doping concentration. Using μ-Raman measurement in cross-section of the 3C-SiC grown samples, it was possible to observe the dependence of the stress and of the quality of the material as a function of the thickness and of the growth rate, due to the variation of the growth rate during the process. In particular, the increase of the growth rate produced both an increase of the stress and a decrease of the material quality. Furthermore, the increase of the doping concentration produced both an increase of the stress and a further deterioration of the crystal quality.
Analysis of Defect-Free Hot Filament CVD-Grown 3C-SiC
Authors: Van Zeghbroeck Bart J. , Brow Ryan , Borsa Tomoko , Bobela David
Published: July 2020

Analysis of hot-filament CVD (HF-CVD) growth of high quality 3C-SiC on micron-sized 3C-SiC mesas is presented. Two types of growth were observed: 1) a relatively slow growth at about 1μm/hour, and 2) an almost three times faster growth, correlated with the presence of domain boundaries in, or adjacent to, the mesas. Both reveal well-defined crystallographic facets and sharp corners between them. The slower growth has been identified to be surface-nucleation-limited, seemingly defect-free, while the faster growth has been identified as being caused by defect-induced step-flow growth. A growth model is presented, yielding a growth rate of 1.18 μm/h for the defect free {111} and (100) plane and 2.8 μm/h for {110} planes.
Exploration of Solid Phase Epitaxy of 3C-SiC on Silicon
Authors: Zielinski Marcin , Monnoye Sylvain , Mank Hugues , Torregrosa Frank , Grosset Gregory , Spiegel Yohann , Portail Marc , Michon Adrien
Published: July 2020

In this contribution we investigate the formation at high temperature of an oriented 3C-SiC seed on various orientations of Si substrates “pre-carbonized” through Plasma Immersion Ion Implantation (PIII) process.
Development of 150-mm 4H-SiC Substrates Using a High-Temperature Chemical Vapor Deposition Method
Authors: Okamoto Takeshi , Kanda Takahiro , Tokuda Yuichiro , Ohya Nobuyuki , Betsuyaku Kiyoshi , Hoshino Norihiro , Kamata Isaho , Tsuchida Hidekazu
Published: July 2020

To reduce the cost of silicon carbide (SiC) substrates, we have developed a high-temperature chemical vapor deposition (HTCVD) method for high-productivity crystal growth. We have conducted research using crystals of diameter 4 inches or less. In order to further reduce the cost, development of a 150-mm substrate has been demanded. With increasing crystal diameter, the occurrence of cracks should be suppressed efficiently. The internal structure of the furnace was designed to reduce the distribution of temperature in the radial direction of the crystal, ultimately reducing the stress responsible for the formation cracks. We demonstrated a 150-mm 4H-SiC substrate without cracks using by HTCVD method.
Etching Rate Profile of C-Face 4H-SiC Wafer Depending on Total Gas Flow Rate of Chlorine Trifluoride and Nitrogen
Authors: Irikura Kenta , Kawasaki Ryohei , Habuka Hitoshi , Takahashi Yoshinao , Kato Tomohisa
Published: July 2020

A 50-mm diameter silicon carbide wafer thinning technique by means of a chemical reaction using a chlorine trifluoride (ClF3) gas was studied accounting for the gas distributor design and the total gas flow rate. The entire etching depth profile could become uniform with the increasing total gas flow rate at the fixed chlorine trifluoride gas concentration. A relationship between the pinhole arrangement of the gas distributor and the local etching rate profile was clarified by comparing the quick calculation and the measurement.
Cost-Efficient High-Throughput Polishing of Silicon Carbide Seed Crystals
Authors: Titov A. , Walters A. , Sasai Hirokazu , Shindo T.
Published: July 2020

Polishing of Silicon Carbide (SiC) seed crystals and substrates to achieve an extremely smooth, level surface, and an optically clear finish takes many surface finishing steps with very long processing times producing a significant amount of slurry waste and utilizing numerous lapping and polishing machines. This paper presents a newly developed cost-efficient SiC polishing process which reduces these operations to two surface finishing steps for achieving an optically clear finish on monocrystalline SiC material where the same size of diamond abrasives for lapping and polishing steps allows to carry out stock removal lapping and polishing processes on a single platform (machine) without concern of cross-contamination and making it as a very cost-efficient and high-throughput polishing process for SiC seed crystals and substrates.
Investigation of Carbon Inclusions in SiC Crystals Grown by PVT Method
Authors: Xie Xue Jian , Yu Jin Ying , Yang Xiang Long , Chen Xiu Fang , Xu Xian Gang , Hu Xiao Bo , Liu Xin Tong , Liu Duo
Published: July 2020

The carbon inclusions in SiC bulk crystals were studied by using optical microscope. The carbon inclusions were classified into three types, namely Type Ⅰ (100~1000 μm), Type Ⅱ (20~50 μm), Type Ⅲ (~5 μm) carbon inclusions based on their different morphologies. In addition, the evolution of these three type carbon inclusions with crystal growth process was traced. It was found that the number of Type Ⅰ and Type Ⅱ carbon inclusions showed declined tendency with crystal growth, while the number of Type Ⅲ carbon inclusions exhibited less dependence on crystal growth. Furthermore, the formation mechanism of carbon inclusions was clarified. This study would give out a better understanding of carbon inclusions, thus contribute to reducing or eliminating carbon inclusions in SiC crystals.
Anomalous Temperature Dependence of the Hall Coefficient of Heavily Al-Doped 4H-SiC Epilayers in the Band Conduction Region
Authors: Matsuura Hideharu , Nishihata Rinya , Takeshita Akinobu , Ogawa Kohei , Imamura Tatsuya , Takano Kota , Okuda Kazuya , Hidaka Atsuki , Ji Shi Yang , Eto Kazuma , Kojima Kazutoshi , Kato Tomohisa , Yoshida Sadafumi , Okumura Hajime
Published: July 2020

We investigate the temperature dependence of the resistivity and Hall coefficient for heavily Al-doped p-type 4H-SiC epilayers with Al concentrations (C_Al) of > 2E19 cm^−3, which are substrates for the collectors of insulated-gate bipolar transistors. The signs of the measured Hall co- efficients (R_H) changed from positive to negative at low temperatures. For epilayers with C_Al values of < 3E19 cm^−3, a negative R_H was observed in the hopping conduction region. In contrast, for epilayers with C_Al values of > 3E19 cm^−3, a negative R_H was observed in not only the hopping conduction region but also the band conduction region, which is a striking feature because the movement of free holes in the valence band should make R_H positive. For an epilayer with C_Al of 1.8E20 cm^−3, the sign of R_H clearly changed three times in the band conduction region. Moreover, the activation energies of the temperature-dependent R_H values were similar to those of the temperature-dependent resistivity in the corresponding temperature ranges, irrespective of the conduction mechanisms (band and hopping conduction).
Comparative Results of Low Temperature Annealing of Lightly Doped N-Layers of Silicon Carbide Irradiated by Protons and Electrons
Authors: Kozlovski Vitalii V. , Korolkov Oleg , Lebedev Alexander A. , Toompuu Jana , Sleptsuk Natalja
Published: July 2020

The influence of low-temperature (up to 400°С) annealing on the current-voltage and capacitance–voltage characteristics of Schottky diodes irradiated with protons with an energy of 15 MeV compared with the results of annealing of structures after irradiation with electrons with an energy of 0.9 MeV has been studied. It was shown that in case of proton irradiation with a dose of 4E13 cm-2 and electron irradiation with a dose of 1E16 cm-2, only partial carrier compensation occurs and the differential resistance is completely determined by the number of carriers in the epitaxial layer. The irradiation method has almost no effect on the direct current dependence on the voltage in the exponential segment. The ideality coefficient remains almost unchanged within 1.03 ÷ 1.04. During annealing after proton irradiation, a large activation energy of the process is required. The temperature of the beginning of annealing process during proton irradiation shifts to a larger value, from 150 °C to 250 °C when compared with electron irradiation. It has been demonstrated that at low doses of proton irradiation, the low-temperature annealing leads to the return to the conduction band of up to 65% of the removed charge carriers. After electron irradiation, low-temperature annealing returns up to 90% of the removed charge carriers to the conduction band. This indicates that at room temperature both proton irradiation as well as electron irradiation introduce both stable and unstable defects but in different proportions.
Improved High Precision Dopant/Carrier Concentration Profiling with Corona-Charge Non-Contact C-V (CnCV)
Authors: Savtchouk Alexandre , Wilson Marshall , D’Amico John , Almeida Carlos , Lagowski Jacek
Published: July 2020

We report significant advancements in corona-based non-contact capacitance-voltage (CnCV) metrology recently developed for comprehensive C-V characterization of SiC and other wide bandgap semiconductors. The technique answers the industries needs for nondestructive, cost-effective C-V dopant monitoring for material and device development and manufacturing control. Excellent precision and matching to mercury probe CV is demonstrated for SiC, Ga2O3, GaN and AlGaN/GaN structures over a concentration range from 1014cm-3 to 2x1019cm-3. The emphasis in the present work is on improvement of CnCV in dopant depth profiling resolution and measurement throughout. This is achieved with a variable charge method that in-situ adjusts corona charging increments in response to changes in dopant concentration. Results are presented for multi-layer epitaxial SiC and for 2DEG in AlGaN/GaN HEMT structures. The latter represents an extreme case of high-low concentration profiling with a transition from 1020electrons/cm-3 in the 2D electron gas to a fully depleted well and dopant concentration in the 1015cm-3 range.
Crystal Separation Method of 6-Inch 4H-SiC Crystal Using Adhesion Shrinkage between a Seed and a Seed Holder in Cooling Process
Authors: Park Jong Hwi , Jang Byung Kyu , Choi Jung Woo , Yang Eunsu , Kim Jung Gyu , Ko Sang Ki , Kyun Myung Ok , Ku Kap Ryeol , Kim Dae Sung , Lee Won Jae
Published: July 2020

6-inch 4H-SiC crystal ingot was successfully separated from a seed holder by the contraction enhancement of adhesive. The resin used as an adhesive with 10~30% in contraction ratio during the cooling was selected. The crack between seed holder and grown SiC crystal was observed to be formed after the cooling procedure and the crystal was easily separated from the seed holder without any machining process for the separation. The warp value and the rocking curve value of SiC crystal grown with modified adhesive was observed to be smaller than those of SiC crystal with conventional method.
Resistivity Measurement of P+-Implanted 4H-SiC Samples Prepared at Different Implantation and Annealing Temperatures Using Terahertz Time-Domain Spectroscopic Ellipsometry
Authors: Ishiji Kotaro , Kawado Seiji , Hirai Yasuharu , Nagamachi Shinji
Published: July 2020

The resistivities of P+-implanted 4H-SiC samples, each prepared at different implantation and annealing temperatures, were measured using terahertz time-domain spectroscopic ellipsometry and compared with the results of the previously reported Raman spectra. The 4H-SiC samples of one group were implanted with P+ at 30 °C, 150 °C, 300 °C, and 500 °C, respectively, and annealed at 1600 °C. The resistivity was found to be approximately 8 mΩ·cm for the samples implanted at 30 and 150 °C and approximately 2 mΩ·cm for the remaining two samples. The 4H-SiC samples of the other group were implanted at 500 °C followed by annealing at 1200 °C, 1400 °C, 1600 °C, and 1800 °C, respectively. The resistivity was measured as 10 mΩ·cm for the sample annealed at 1200 °C and 3.0−1.8 mΩ·cm for the remaining three samples. These resistivity values are correlated with the Raman peak widths that reflect the lattice disorder.
Investigation of the Influence of Structural Defects on the PL Spectra in n-3C-SiC
Authors: Shakhov Lev V. , Lebedev Alexander A. , Seredova Natalia. V. , Lebedev Sergey P. , Kozlovski Vitalii V. , Zubov Alexander V. , Nikitina Irina P.
Published: July 2020

The photoluminescence spectra were studied in 3C-SiC / 4H-SiC heterostructures and single crystals of 3C-SiC. It was shown that 3C-SiC epitaxial layers grown on 4H-SiC substrates have significantly less structural perfection than 3C-SiC single crystals. It was found that doping with aluminum leads to the appearance of characteristic photoluminescence (PL) both in the epitaxial layers and in 3C-SiC single crystals. At the same time, the irradiation of the epitaxial layers does not lead to the appearance of “defective PL (DFL), as is observed for single crystals. It was suggested that the twin boundaries existing in 3C-SiC epitaxial layers could serve as getters of radiation defects that are components of donor – acceptor pairs (DAP) responsible for DFL.
A New Technique for Analyzing Defects in Silicon Carbide Devices: Electrically Detected Electron Nuclear Double Resonance
Authors: Waskiewicz Ryan J. , Manning Brian , McCrory Duane J. , Lenahan Patrick M.
Published: July 2020

We show that electrically detected electron nuclear double resonance (EDENDOR) can be detected with relatively high signal-to-noise ratios in fully processed 4H-SiC bipolar junction transistors (BJTs). We observe EDENDOR of nitrogen interacting with recombination center defects in the depletion region of forward-biased emitter-base junctions of these devices at room temperature. Our results indicate that EDENDOR has great potential in the investigation of SiC-based devices specifically, as well as in the investigation of solid-state devices based upon other material systems.
Modified Hot-Zone Design of Growth Cell for Reducing the Warpage of 6”-SiC Wafer
Authors: Jang Byung Kyu , Park Jong Hwi , Choi Jung Woo , Yang Eunsu , Kim Jung Gyu , Ko Sang Ki , Kyun Myung Ok , Ku Kap Ryeol , Jang Yeon Suk , Lee Won Jae
Published: July 2020

The modified hot-zone design, consisting of a new design and new materials for the backside of SiC seed holder was adopted for reducing stress in grown SiC crystal ingot and for reducing the warpage of 6-inch SiC wafer. Crucible lid on the backside of SiC seed holder was designed to be movable during the growth process. Based on the warp value and mapping measurement of FWHM (Full width at half maximum) value in X-ray rocking curve, the crystal quality of SiC crystals grown with new hot-zone design was observed to be better than conventional design.
From Wafers to Bits and Back again: Using Deep Learning to Accelerate the Development and Characterization of SiC
Authors: Leonard Robert , Conrad Matthew , van Brunt Edward , Giles Jeffrey , Hutchins Ed , Balkas Elif
Published: July 2020

A non-destructive, fast and accurate extended defect counting method on large diameter SiC wafers is presented. Photoluminescence (PL) signals from extended defects on 4H-SiC substrates were correlated to the specific etch features of Basal Plane Dislocations (BPDs), Threading Screw Dislocations (TSDs), and Threading Edge Dislocations (TED). For our non-destructive technique (NDT), automated defect detection was developed using modern deep convolutional neural networks (DCNN). To train a robust network, we used our large volume data set from our selective etch method of 4H-SiC substrates, already established based on definitive correlations to Synchrotron X-Ray Topography (SXRT) [1]. The defect locations, classifications and counts determined by our DCNN correlate with the subsequently etch-delineated features and counts. Once our network is sufficiently trained we will no longer need destructive methods to characterize extended defects in 4H-SiC substrates.
Current-Mode Deep Level Spectroscopy of Vanadium-Doped HPSI 4H-SiC
Authors: Alfieri Giovanni , Kranz Lukas , Mihaila Andrei
Published: July 2020

SiC has currently attracted the interest of the scientific community for qubit applications. Despite the importance given to the properties of color centers in high-purity semi-insulating SiC, little is known on the electronic properties of defects in this material. In our study, we investigated the presence of electrically active levels in vanadium-doped substrates. Current mode deep level transient spectroscopy, carried out in the dark and under illumination, together with 1-D simulations showed the presence of two electrically active levels, one associated to a majority carrier trap and the other one to a minority carrier trap. The nature of the detected defects has been discussed in the light of the characterization performed on low-energy electron irradiated substrates and previous results found in the literature.
4H-SiC Epi-Ready Substrate Qualification by Using Mirror Electron Microscope Inspection System
Authors: Hasegawa Masaki , Ohira Kentaro , Kaneoka Noriyuki , Ogata Tomohiko , Onuki Katsunori , Kobayashi Kenji , Osanai Tsutom , Masumoto Keiko , Senzaki Junji
Published: July 2020

Crystal damage beneath the surface remaining after chemo-mechanical polishing (CMP) and basal plane dislocations (BPDs) of 4H-SiC epi-ready substrates have been inspected by using a mirror electron microscope inspection system non-destructively. Distributions of crystal damage and BPDs as well as their average densities are estimated by acquiring 80-μm square mirror electron images at positions distributed with an equal pitch over a substrate (“Discrete point set inspection”). Although the total inspected area is less than 1% of the entire substrate area, the inspection results for nine commercially available wafers reveal that there are large differences in surface polishing quality and BPD density between them. Evaluation on an epitaxial layer with a thickness of 10 μm grown on one of the inspected substrates indicated that correlation between distribution of the crystal damages on the substrate and that of bunched steps on the epitaxial layer surface.
BPD-TED Conversion in the SiC Substrate after High-Temperature Si-VE
Authors: Sudoh Yusuke , Kitabatake Makoto , Kaneko Tadaaki
Published: July 2020

We propose the Si-Vapor Etching (Si-VE), which is thermal chemical etching process, as epi-ready treatment for Silicon Carbide (SiC). In this work, we report the evaluation results of BPD-TED conversion by Si-VE treatment using repeated KOH etching process. This method makes it possible to observe BPD-TED conversion in a very shallow surface region of the SiC substrate. 80% of BPDs is converted to TEDs with a depth of more than 80nm under optimized Si-VE 2000°C conditions. Furthermore, 53% of BPDs were converted to TEDs with 140nm or more depth, which has been confirmed under optimized 1800°C Si-VE conditions.
TEM Studies on the Microstructure of m-Face Grown 4H-SiC by Solution Growth
Authors: Takahashi Junro , Kawaguchi Kotaro , Kusunoki Kazuhiko , Ueyama Tomoyuki , Kamei Kazuhito
Published: July 2020

We have studied the microstructure of the growth surface of the 4H-SiC grown by the m-face solution growth. Atomic Force Microscopy (AFM) revealed the micro-striped morphology with the asperity of several nm in the band-like morphology region. The cross-sectional Transmission Electron Microscopy (XTEM) showed that the growth surface consisted of a bunch of nanofacets and vicinal surface. This peculiar morphology is totally different from that of conventional spiral growth on c-face, which can be closely related with the growth mechanism of the m-face solution growth.
Structural Characterization of Prismatic Stacking Faults of Two Types of Carrot Defects in 4H-SiC Epi Wafers
Authors: Sako Hideki , Ohira Kentaro , Kobayashi Kenji , Isshiki Toshiyuki
Published: July 2020

Two types of carrot defects with and without a shallow pit were found by mirror projection electron microscopy (MPJ) inspection in 4H-SiC epi wafer. Surface morphology and cross-sectional structure of prismatic stacking faults (PSFs) were investigated using MPJ and atomic force microscopy (AFM), transmission electron microscopy (TEM) and high-resolution scanning transmission electron microscopy (STEM). The depths of the surface grooves due to the PSFs, the stacking sequences around the PSFs and the structure of the Frank-type stacking faults which were connected to the PSFs were different. We discuss the difference between the two types of carrot defects.
Formation of Double Shockley Stacking Faults in Heavily Nitrogen Doped 4H-SiC Crystal with Reduction of Residual Stress around Scratch Damage
Authors: Sugiyama Naohiro , Mitani Takeshi , Kamata Isaho , Kato Tomohisa , Tsuchida Hidekazu , Okumura Hajime
Published: July 2020

The scratch damage that caused the generation of double Shockley stacking faults (DSFs) in heavily nitrogen doped 4H-SiC crystal was investigated quantitatively. Scratch tests were carried out on 4H-SiC substrates with a nitrogen concentration of 2.6 × 1019 cm-3. A residual tensile stress of 40 MPa was detected around the scratch loaded at 30 mN with a diamond tip. DSFs were generated from this scratch by annealing at 1100°C for 2 h in Ar atmosphere. After annealing, the residual stress around the scratch was reduced to a tensile stress of 10 MPa. This result suggests that the reduction of residual stress around the scratch coincided with the formation of DSFs.
Evaluation of Suppressing Forward Voltage Degradation by Using a Low BPD Density Substrate or an Epitaxial Wafer with an HNDE
Authors: Nishihara Yoshitaka , Kamei Koji , Momose Kenji , Osawa Hiroshi
Published: July 2020

Forward voltage degradation is a crucial problem that must be overcome if we are to fabricate a metal-oxide semiconductor field-effect transistor (MOSFET) including a pin diode (PND) as a body diode in a silicon carbide (SiC). Previously, the basal plane dislocation (BPD) in a SiC substrate have been reduced to suppress bipolar degradation. On the other hand, an highly N-doped epilayer (HNDE) was recently fabricated that enhances the minority carrier recombination before the carrier arrives at the substrate. Although both approaches can reduce the Vf shift caused by the degradation, they should be used under different substrate conditions. When a substrate with a high BPD density is used for epitaxial growth, an HNDE is needed to realize a high-quality epitaxial wafer; however, the HNDE should not be formed on a substrate with a low BPD density.
Investigation of Bipolar Degradation of 1.2 kV BJTs under Different Current and Temperature Conditions
Authors: Rugen Sarah , Sundaresan Siddarth G. , Singh Ranbir , Kaminski Nando
Published: July 2020

Bipolar silicon carbide devices are attractive for high power applications offering high voltage devices with low on-state voltages due to plasma flooding. Unfortunately, these devices suffer from bipolar degradation, which causes a significant degradation of the on-state voltage. To explore the generation of stacking faults, which cause the degradation, the impact of the current density and temperature on bipolar degradation is investigated in this work. The analysis is done by stressing the base-collector diode of 1.2 kV bipolar junction transistors (BJTs) as well as the BJTs in common-emitter mode operation with different current densities at different temperatures.
Dislocation Vector Analysis Method of Deep Dislocation Having C-Axis Segment in Diamond
Authors: Shikata Shinichi , Akashi Naoya
Published: July 2020

X-ray topography is an effective tool to investigate dislocations in semiconductor crystals. Due to low X-ray absorption coefficients of diamond, X-rays can penetrate deep into the crystal. Thus, deep three-dimensional (3D) dislocations are projected on two-dimension (2D) film, which makes dislocation analysis particularly challenging. Dislocation vectors from the films obtained using a set of the same diffraction vectors were identified using topographical and geometrical analyses. The depth and position of the dislocations in a crystal that was projected on a film were determined using geometrical relationship. The proposed analysis method was verified by analyzing several dislocations using four <404> diffraction films. The types of dislocation were identified through Burgers vector analysis.
4H-SiC Power VDMOSFET Manufacturing Utilizing POCl3 Post Oxidation Annealing
Authors: Ju Yanrui , Bouvet Didier , Stark Roger , Woerle Judith , Grossner Ulrike
Published: July 2020

A novel POCl3 post-oxidation annealing recipe was developed. The interface trap density (Dit) is extracted by the C-ΨS method close to conduction band edge. The performance of the POCl3-treated oxide has been analyzed based on current density-electric field (J-E) measurements. A comprehensive and practical 4H-SiC power VDMOSFET manufacturing traveler has been designed. The power MOSFET that was fabricated based on this traveler exhibits less than half of the on-resistance and shows improved interface characteristics compared to a similarly designed commercial power MOSFET.
Compatibility of POCl3 Gate Process with the Fabrication of Vertical 4H-SiC MOSFETs
Authors: Watanabe Tomokatsu , Noguchi Munetaka , Tomohisa Shingo , Miura Naruhisa
Published: July 2020

We used the POCl3 gate technique for the fabrication of 4H-SiC vertical MOSFETs, and examined its effect on the VTH-RON tradeoff and the compatibility with device fabrication. The gate oxide film was formed by thermal dry O2 oxidation followed by POCl3 or NO annealing. The POCl3 process reduced RON by about 30% compared with the NO process for the ones having VTH of 1.1 V, being attributed to the channel mobility enhancement. Moreover, the improvement was more effective for higher VTH designs. The conventional thermal treatment after the gate process considerably spoiled the channel mobility improvement brought by the POCl3 annealing and strengthened negative charge trapping in the gate oxide. The presumed extra-formed defects also affected the EOX dependence of tBD on the TDDB tests, being expected to shorten the gate oxide lifetime under practical device operation stress. Successful insertion of the POCl3 process into production lines depends upon careful low-temperature post processing.