bluuebunny/crossref_metadata_2025 huggingface dataset:
New Efficient Canal of THz Emission from SiC Natural Superlattices in Conditions of Wannier-Stark Localization
Authors: Sankin Vladimir Ilich , Andrianov Alexander V. , Petrov Alexey G. , Nagalyuk Sergey , Shkrebiy Pavel P. , Zachar'in A.O.
Published: May 2017

The comprehensive study of the terahertz electroluminescence caused by the Bloch oscillations of the electrons in the natural superlattices of 8H-, 6H-SiC with strong electrical field applied along the natural superlattices axis is represented. The electroluminescence spectra become much broader when the bias field exceeds substantially the threshold field of the Bloch oscillations. This spectral broadening can be explained by an appearance of a new spectral line that is much wider and its maximum is localized at higher energy than lines induced by Bloch oscillations. This line has no link with the Bloch oscillations mechanism and it is a result of the presumed changes in the SiC conduction band with complex electron spectrum structure by applied electrical field.
Point Defects Investigation of High Energy Proton Irradiated SiC p+-i-n Diodes
Authors: Alfieri Giovanni , Mihaila Andrei , Nipoti Roberta , Puzzanghera Maurizio , Sozzi Giovanna , Godignon Philippe , Millán José
Published: May 2017

We performed deep level transient spectroscopy (DLTS), in capacitance, constant-capacitance and current mode, on 5 MeV proton irradiated 4H-SiC p+-i-n diodes. The study has revealed the presence of several majority and minority traps, ranging in the 0.4-1.6 eV below the conduction band edge and in the 0.4-1.5 eV above the valence band edge. We present a comparison of the results obtained with the three modes and discuss the nature of the detected traps, in the light of previous results found in the literature. At last, the impact of the irradiation on the minority carrier lifetime is evaluated by electrical measurements.
Comparative Study of p-Type 4H-SiC Grown on n-Type and Semi Insulating 4H-SiC Substrates
Authors: Contreras Sylvie , Konczewicz Leszek , Arvinte Roxana , Ben Messaoud Jaweb , Wang Tian Lin , Peyre Hervé , Chassagne Thierry , Zielinski Marcin , Juillaguet Sandrine
Published: May 2017

Comparative study of p-type 4H-SiC epitaxial layers grown simultaneously on two different 4H-SiC substrates, namely n-type and semi-insulating have been done by different structural, optical and electrical experimental techniques.
DLTS Study on Al+ Ion Implanted and 1950°C Annealed p-i-n 4H-SiC Vertical Diodes
Authors: Ayedh Hussein M. , Puzzanghera Maurizio , Svensson Bengt Gunnar , Nipoti Roberta
Published: May 2017

A vertical 4H-SiC p-i-n diode with 2×1020cm-3 Al+ implanted emitter and 1950°C/5min post implantation annealing has been characterized by deep level transient spectroscopy (DLTS). Majority (electron) and minority (hole) carrier traps have been found. Electron traps with a homogeneous depth profile, are positioned at 0.16, 0.67 and 1.5 eV below the minimum edge of the conduction band, and have 3×10-15, 1.7×1014, and 1.8×10-14 cm2 capture cross section, respectively. A hole trap decreasing in intensity with decreasing pulse voltage occurs at 0.35 eV above the maximum edge of the valence band with 1×1013 cm2 apparent capture cross section. The highest density is observed for the refractory 0.67 eV electron trap that is due to the double negative acceptor states of the carbon vacancy.
Micro-Raman Scattering Study of Strain Fields in Homo-Epitaxial Layer on Nitrogen-Doped 4H-SiC Substrate
Authors: Fukunaga Daisuke , Ohtani Noboru , Katsuno Masakazu , Sato Shinya , Tsuge Hiroshi , Fujimoto Tatsuo
Published: May 2017

The strain fields in a 4H-SiC homo-epitaxial layer deposited on a nitrogen-doped 4H-SiC substrate were studied using Raman scattering microscopy. The cross-sectional (1-100) and (11-20) surfaces of the epitaxial substrate were examined through the peak shifts of several Raman-active phonon modes for 4H-SiC, and tensile strain was found along the direction of 4° off the c-axis at the epilayer/substrate interface. The effect of the facet trace in the substrate, which has a higher nitrogen concentration than the other parts of the substrate, was also studied. The tensile strain at the epilayer/substrate interface was found to be hardly enhanced for the epilayer deposited on the facet trace.
Point Contact Current Voltage Measurements of 4H-SiC Samples with Different Doping Profiles
Authors: Kocher Matthias , Niebauer Michael , Rommel Mathias , Haeublein Volker , Bauer Anton J.
Published: May 2017

Point contact current voltage (PCIV) measurements were performed on 4H-SiC samples, both for n- an p-doped epitaxial layers as well as samples with rather shallow doping profiles realized by N- or Al-implantation in a range from 1016 cm-3 to 1019 cm-3. Surface preparation and measurement parameters were investigated in order to determine their influence on the measured resistance profiles. Furthermore depth profile measurements were performed on both an epitaxial layer as well as on implanted samples. These depth profiles could be measured reproducibly and showed good agreement with expected profiles for Al-implanted samples as well as for epitaxial layer whereas for N-implanted samples deviations between measured and expected profiles could be observed. It could be proven that PCIV profiling technique is a promising method for characterizing doped profiles in 4H-SiC, especially on Al-implanted samples.
Effect of Neutron Irradiation on SiC Etching in KOH Melt
Authors: Mokhov Evgeniy , Kazarova Olga P. , Nagalyuk Sergey
Published: May 2017

The effect of reactor neutron irradiation on the SiC crystals etching rate in KOH melt has been investigated. It is shown that at high doses of irradiation (1019 - 1021 neutrons/cm2) the SiC etching rate sharply increases, especially in the [0001] Si direction, leading to essential reduction of orientation anisotropy of polar {0001} faces etching. The increased rate of irradiated crystals etching remains after high-temperature annealing, up to the temperatures of 1400 – 1600 °C. The results are explained by the presence of meta-stable clusters of radiation defects which are the centers of increased chemical activity in the irradiated crystals.
Bulk Growth of Low Resistivity n-Type 4H-SiC Using Co-Doping
Authors: Suo Hiromasa , Eto Kazuma , Kato Tomohisa , Kojima Kazutoshi , Osawa Hiroshi , Okumura Hajime
Published: May 2017

The growth of n-type 4H-SiC crystal was performed by physical vapor transport (PVT) growth method by using nitrogen and aluminum (N-Al) co-doping. Resistivity of N-Al co-doped 4H-SiC was as low as 5.8 mΩcm. The dislocation densities of N-Al co-doped substrates were evaluated by synchrotron radiation X-ray topography (SXRT). In addition, epitaxial growth was performed on the N-Al co-doped substrates by chemical vapor deposition (CVD). No double Shockley type stacking fault was observed in the epitaxial layer.
Photoluminescence Characterization of Carrier Recombination Centers in 4H-SiC Substrates by Utilizing below Gap Excitation
Authors: Kondo Keitaro , Kamata N , Yaguchi Hiroyuki , Yagi Shuhei , Fukuda Takeshi , Honda Zentaro
Published: May 2017

Though the crystal growth technology of SiC is improving steadily, it is still crucial to reduce crystalline defects which act as carrier recombination (CR) centers and deteriorate device performance. We detected CR centers in a p-type 4H-SiC substrate by observing the intensity change of photoluminescence due to the addition of a below-gap excitation (BGE) light of 0.93[eV]. We noticed the temperature and the BGE density dependence of band edge (BE) emission in addition to donor acceptor pair (DAP) emission and discriminated the temperature effect from that of BGE. The BGE density dependence of the PL intensity quenching is different among the BE emission, B0- and C0-lines of the DAP, respectively. It gives us an important clue for understanding CR mechanisms inside the bandgap of SiC.
Solvent Design for High-Purity SiC Solution Growth
Authors: Harada Shunta , Hatasa Goki , Murayama Kenta , Kato Tomohisa , Tagawa M. , Ujihara Toru
Published: May 2017

In order to design a solvent for high-purity SiC solution growth, the impurity incorporation and the carbon solubility of various solvent materials have been investigated. Among the transition metal elements, the impurity elements of Cr, Ti, V and Hf are more readily incorporate during the solution growth than the other transition metal elements. The thermodynamic calculation revealed that the Y-Si solvent has relatively large carbon solubility, which is comparable to the Cr-Si and Ti-Si solvents often used in the solution growth of bulk SiC crystals. From these results, the Y-Si solvent is expected to be a suitable solvent for the high-purity SiC solution growth. Furthermore, we have demonstrated that the Y-Si solvent can achieve lower incorporation of metal impurity in the grown crystal than the Cr-Si solvent maintaining the growth rate.
Re-Investigation of SiC/SiO2 Interface Passivation by Nitrogen Annealing
Authors: Peng Zhao Yang , Wang Yi Yu , Shen Hua Jun , Bai Yun , Tang Yi Dan , Chen Xi Ming , Li Chengzhan , Liu Ke An , Liu Xin Yu
Published: May 2017

Effect of nitrogen annealing on SiC/SiO2 interface properties was comparatively investigated for SiC MOS capacitors. Interface properties were characterized by normalized parallel conductance and interface state density value, and dielectric strength was evaluated by the electric-field-to-breakdown (Ebd). The results exhibited that both fast and slow states were present at the nitrogen-annealed samples’ parallel conductance characteristics. Thus, we could conclude that nitrogen annealing led to incomplete nitridation of SiC/SiO2 interface. Based on the results, nitridation mechanism was simply analyzed. It seemed that the nitridation process started from near conduction band, extending till to mid-band-gap. Besides, when the samples underwent higher temperature nitrogen annealing, more slow states were converted into fast ones, indicating that higher annealing temperature could lead to more effective nitridation. It was suggested that nitrogen annealing resulted in incomplete nitridation of SiC/SiO2 interface regardless of oxide thickness and that this process was limited to the annealing temperature. The higher the annealing temperature was, the more effective the nitridation effects were.
Structure and Surface Morphology of Thermal SiO2 Grown on 4H-SiC by Metal-Enhanced Oxidation Using Barium
Authors: Chanthaphan Atthawut , Katsu Yoshihito , Hosoi Takuji , Shimura Takayoshi , Watanabe Heiji
Published: May 2017

Surface morphology and electrical properties of silicon dioxide (SiO2) on 4H-SiC substrates formed by metal-enhanced oxidation (MEO) using barium (Ba) atoms were systematically investigated. It was found that severe surface roughening caused by Ba-MEO can be suppressed by using SiO2 capping prior to MEO. The Ba atoms at the SiO2/SiC interface were found to diffuse to the oxide surface through the deposited SiO2 capping layer, and then the Ba density reduced to ~1014 cm-2 before stable MEO. The resulting SiO2/SiC interface showed the reduced interface state density but the insulating property of the oxides was significantly degraded.
Combined N2O and Phosphorus Passivations for the 4H-SiC/SiO2 Interface with Oxide Grown at 1400°C
Authors: Rong Hua , Sharma Yogesh K. , Mawby Philip  Andrew
Published: May 2017

Phosphorus (P) passivation is more effective than N2O passivation in improving the 4H-SiC/ SiO2 interface by reducing the number of traps at the 4H-SiC/SiO2 interface. This paper investigated the effect of combined N2O and phosphorus POA on the 4H-SiC/SiO2 interface with oxides grown at 1400°C and used in the fabrication of MOS capacitors and FETs. These fabricated devices are also compared with the ones which have been N2O and P passivations only. Results demonstrated that the phosphorus passivation technique provides the highest peak field-effect mobility for 4H-SiC MOSFETs (60 cm2/V.s), which is about 5 times higher than the value obtained for devices with N2O annealing. The combined N2O and phosphorus passivation technique, however, has shown a slight decrease in the peak field effect mobility value compared to the phosphorus passivation technique, but it is still much higher than the N2O passivation technique (12 cm2/V.s).
Enhanced-Oxidation and Interface Modification on 4H-SiC(0001) Substrate Using Alkaline Earth Metal
Authors: Muraoka Kosuke , Sezaki Hiroshi , Ishikawa Seiji , Maeda Tomonori , Sato Tadashi , Kikkawa Takamaro , Kuroki Shin Ichiro
Published: May 2017

Enhanced-oxidation of 4H-SiC and interface modification with BaO2 was investigated. The enhanced oxidation of 4H-SiC was drastically dependent on pre-deposited BaO2 thickness. At the oxidation time of 300 min, oxide thicknesses for BaO2 of 2.8 nm and 7.8 nm were 91.8 nm and 26.2 nm, respectively. The physical state of Ba in the oxide was investigated by XPS and 2D-GIXD. At thick BaO2 with a thickness of over 6.4 nm, bridged oxygen and non-bridged oxygen were observed in O1s state. This results shows barium silicate was formed in SiO2 at BaO2 thickness of over 6.4 nm.
4H-SiC Trench Structure Fabrication with Al2O3 Etching Mask
Authors: Dai Tian Xiang , Mohammadi Z. , Russell Stephen , Fisher Craig A. , Jennings Michael R. , Mawby Philip  Andrew
Published: May 2017

Trench structure etching is one of the most important processes for the fabrication of 4H-SiC Trench MOSFETs. This paper introduced Al2O3 as an etching mask for the fabrication of trench structures. The effect of dry etching parameters to the shape of trench structures were studied systematically. Micro trenches were successfully eliminated from trench structure etching process and preliminary trench MOSFET test structures were fabricated and characterized.
Improving Mechanical Strength and Surface Uniformity to Prepare High Quality Thinned 4H-SiC Epitaxial Wafer Using Si-Vapor Etching Technology
Authors: Torimi Satoshi , Ashida Koji , Yabuki Norihito , Shinohara Masato , Sakaguchi Takuya , Teramoto Yoji , Nogami Satoru , Kitabatake Makoto , Kaneko Tadaaki
Published: May 2017

As a new thinning and surface planarizing process of Silicon Carbide (SiC) wafer, we propose the completely thermal-chemical etching process; Si-vapor etching (Si-VE) technology. In this work, the effects of mechanical strength and surface step-terrace structure by Si-VE are investigated on the 4° off-axis 4H-SiC (0001) Si-face substrates. The indentation hardness of Si-VE surface is superior to the conventional chemo-mechanical polishing (CMP) surface even after epitaxial growth. The transverse strength of thinned Si-VE substrate is also superior to the conventional mechanically ground substrate. The surface step-terrace structures are observed by the low energy electron channeling contrast (LE-ECC) imaging technique. The latent scratch causes bunched step lines (BSLs) with various inhomogeneous step morphologies only on the CMP surface.
A Method to Adjust Polycrystalline Silicon Carbide Etching Rate Profile by Chlorine Trifluoride Gas
Authors: Nakagomi Ken , Okuyama Shogo , Habuka Hitoshi , Takahashi Yoshinao , Kato Tomohisa
Published: May 2017

A method to adjust the polycrystalline SiC etching rate was studied taking into account the chlorine trifluoride gas transport. The etching rate profile over the 50-mm-diameter SiC wafer could be made symmetrical by means of the wafer rotation. By activating and indeactivating the pin-holes at the various positions of the gas distributor, the etching rate profile could be locally adjusted.
Suppression of the Forward Degradation in 4H-SiC PiN Diodes by Employing a Recombination-Enhanced Buffer Layer
Authors: Tawara Takeshi , Miyazawa Tetsuya , Ryo Mina , Miyazato Masaki , Fujimoto Takumi , Takenaka Kensuke , Matsunaga Shinichiro , Miyajima Masaaki , Otsuki Akihiro , Yonezawa Yoshiyuki , Kato Tomohisa , Okumura Hajime , Kimoto Tsunenobu , Tsuchida Hidekazu
Published: May 2017

Application of highly N-doped buffer layers or a (N+B)-doped buffer layer to PiN diodes to suppress the expansion of Shockley stacking faults (SSFs) from the epilayer/substrate interface was studied. These buffer layers showed very short minority carrier lifetimes of 30–200 ns at 250°C. The PiN diodes were fabricated with buffer layers of various thicknesses and were then tested under high current injection conditions of 600A/cm2. The thicker buffer layers with shorter minority carrier lifetimes demonstrated the suppression of SSFs expansion and thus that of diode degradation.
150mm Silicon Carbide Selective Embedded Epitaxial Growth Technology by CVD
Authors: Hara Kazukuni , Fujibayashi Hiroaki , Takeuchi Yuuichi , Omae Shoichiro
Published: May 2017

In this work, we have developed a selective embedded epitaxial growth process on 150-mm-diameter wafer by vertical type hot wall CVD reactor with the aim to realize the all-epitaxial 4H-SiC MOSFETs [1, 2, 3, 4, 5]. We found that at elevated temperature and adding HCl, the epitaxial growth rate at the bottom of trench is greatly enhanced compare to growth on the mesa top. And we obtain high growth rate 7.6μm/h at trench bottom on 150mm-diameter-wafer uniformly with high speed rotation (1000rpm).
Demonstration of 13-kV Class Junction Barrier Schottky Diodes in 4H-SiC with Three-Zone Junction Termination Extension
Authors: Kitai Hidenori , Hozumi Yasuo , Shiomi Hiromu , Furumai Masaki , Omote Kazuhiko , Fukuda Kenji
Published: May 2017

The static and dynamic characteristics of 13-kV class 4H-SiC junction barrier Schottky (JBS) diodes with a three-zone junction termination extension (JTE) are presented. Using an anisotropy breakdown model, technology computer-aided design simulation of devices with a three-zone JTE agrees well with the obtained experimental results, correctly predicting a sharp drop in blocking voltage at high JTE acceptor concentrations. The forward voltage of the JBS diode at 75°C and a forward current of 500 mA is reduced to approximately one-ninth by that of 13 series-connected 1000-V Si PiN diodes. This suggests that conduction losses of traditional high-voltage circuits which conventionally use series-connected devices can be drastically reduced by replacing the series-connected devices with a single 13-kV class SiC JBS diode. Moreover, the reverse recovery current waveform of the 13-kV class SiC JBS diode shows that these diodes have lower reverse recovery losses than a 13-kV SiC PiN diode.
Effect of Neutron Irradiation on Current-Voltage Characteristics of Packaged Diodes Based on 6H-SiC pn Structures
Authors: Strel'chuk Anatoly M. , Gromov V.T. , Zelenin Viktor V. , Kuznetsov A.N. , Lebedev Alexander A. , Orlov N.G. , Savkina N.S. , Shukailo V.P.
Published: May 2017

Neutron irradiation (~1 MeV, dose 1014-5.6∙1015 neutron/cm2) of packaged diodes based on 6H-SiC pn structures (with the base n-layer doped to ~5∙1016 cm-3) has been studied. In addition to the well-known rise in the series resistance of the diodes, the effect of a partial suppression of the excess current in both forward-and reverse-biased diodes and that of an increase in the recombination current, probably associated with the decrease in the nonequilibrium carrier lifetime, were discovered and discussed. These effects are common to 6H-and 4H-SiC pn structures.
Analysis of Trench-Filling Epitaxial Growth of 4H-SiC Based on Continuous Fluid Approximation Including Gibbs-Thomson Effect
Authors: Mochizuki Kazuhiro , Ji Shi Yang , Kosugi Ryoji , Kojima Kazutoshi , Yonezawa Yoshiyuki , Okumura Hajime
Published: May 2017

Trench-filling epitaxial growth of 4H-SiC was analyzed based on a simulation model for continuous fluid approximation including the Gibbs-Thomson effect. With the use of the radii of curvature at the top and bottom of the trenches, the proposed model well reproduced the measured dependence of the growth rate on the trench pitch (L) in the case of narrow (L ≤ 6.0 μm) trenches.
3.3 kV 4H-SiC DMOSFET with Highly Reliable Gate Insulator and Body Diode
Authors: Shima Akio , Shimizu Haruka , Mori Yuki , Sagawa Masakazu , Konishi Kumiko , Fujita Ryusei , Ishigaki Takashi , Tega Naoki , Kobayashi Keisuke , Sato Shintaroh , Shimamoto Yasuhiro
Published: May 2017

We investigated improvement ways of to overcome these reliability issues in a 3.3 kV 4H-SiC DMOSFET. JFET doping with (i) narrow width and (ii) deeper depth than that of the p-well region successfully reduced the electric field in the gate insulator and the on-voltage simultaneously. We achieved a low Ron of 26 mΩcm2 at a Vg of +15 V and 150 °C. And highly reliable chips of 0.1 Fit were also achieved both at a positive and negative gate bias of +15 V/ -8 V with MTTF of intrinsic lifetime over 20 years at 3 MV/cm. BTI characterstics both in positive and negative biases also proved reliability over 20 years. The body diode showed stable behavior under forward current operation which is suitable for an external diode-less power module.
Feasibility of SiC Threshold Voltage Drift Characterization for Reliability Assessment in Production Environments
Authors: Habersat Daniel B. , Green Ronald , Lelis Aivars J.
Published: May 2017

We reviewed the practical challenges of assessing the threshold voltage drift of SiC MOSFETs in the context of a commercial production environment and qualification standards. Stress bias interruption is a key challenge owing to the rapid recovery of threshold following the removal of bias and the necessity of delays and bias interruptions when qualifying device lots. The test standards in use proscribe how such interruptions should be handled using a re-application of the stress once the device is ready for characterization but these turn out to be completely inadequate when dealing with the trapping mechanics of SiC MOS. Our data indicates that a relatively short stress re-application can be successful at restoring a majority of the threshold voltage drift, scaling with the square root of the interruption time. Additionally, it is important to re-apply the stress bias even for brief interruptions since the threshold recovers so quickly (as opposed to the 96-hour stress interrupt window that is allowed before any re-application is necessary in JESD22 A-108D).
Impact of Channel Mobility Improvement Using Boron Diffusion on Different Power MOSFETs Voltage Classes
Authors: Soler Victor , Cabello Maria , Berthou Maxime , Montserrat Josep , Rebollo José , Godignon Philippe , Bianda Enea , Mihaila Andrei
Published: May 2017

SiC planar VDMOS of three voltages ratings (1.7kV, 3.3kV and 4.5kV) have been fabricated using a Boron diffusion process into the thermal gate oxide for improving the SiO2/SiC interface quality. Experimental results show a remarkable increase of the effective channel mobility which increases the device current capability, especially at room temperatures. At high temperatures, the impact of the Boron treatment is lower since the major contribution of the drift layer to the on-resistance. In addition, the intrinsic body diode characteristics approximate to that of an ideal PiN diode, and the blocking capability is not compromised by the use of Boron for the gate oxide formation.
Comprehensive and Detailed Study on the Modeling of Commercial SiC Power MOSFET Devices Using TCAD
Authors: Müting Johanna , Kakarla Bhagyalakshmi , Grossner Ulrike
Published: May 2017

The main scattering mechanisms reducing the channel mobility and thus the typical performance of a SiC power MOSFET are reviewed. It is demonstrated that the Poisson equation within the drift-diffusion model is able to account for the effects of ionized impurity scattering. Furthermore, a correlation between the size of macro-or nanosteps at the SiC/SiO2 interface and the corresponding fitting parameter within the Lombardi surface roughness model is established. By qualitatively reproducing the typical performance of a commercial SiC power MOSFET a baseline for the TCAD modeling of power MOSFETs is provided.
Experimentally Observed Electrical Durability of 4H-SiC JFET ICs Operating from 500 °C to 700 °C
Authors: Neudeck Philip G. , Spry David J. , Chen Liang Yu , Lukco Dorothy , Chang Carl W. , Beheim Glenn M.
Published: May 2017

Prolonged 500 °C to 700 °C electrical testing data from 4H-SiC junction field effect transistor (JFET) integrated circuits (ICs) are combined with post-testing microscopic studies in order to gain more comprehensive understanding of the durability limits of the present version of NASA Glenn's extreme temperature microelectronics technology. The results of this study support the hypothesis that T ≥ 500 °C durability-limiting IC failure initiates with thermal stress-related crack formation where dielectric passivation layers overcoat micron-scale vertical features including patterned metal traces.
Improved Switching Characteristics Obtained by Using High-k Dielectric Layers in 4H-SiC IGBT: Physics-Based Simulation
Authors: Naidu Vidya , Kotamraju Siva
Published: May 2017

Silicon Carbide (SiC) based MOS devices are one of the promising devices for high temperature, high switching frequency and high power applications. In this paper, the static and dynamic characteristics of an asymmetric trench gate SiC IGBT with high-k dielectrics- HfO2 and ZrO2 are investigated. SiC IGBT with HfO2 and ZrO2 exhibited higher forward transconductance ratio and lower threshold voltage compared to conventionally used SiO2. In addition, lower switching power losses have been observed in the case of high-k dielectrics due to reduced tail current duration.
Improvement of Quality of Thick 4H-SiC Epilayers
Authors: Miyasaka Akira , Kojima Kazutoshi , Momose Kenji , Osawa Hiroshi , Okumura Hajime
Published: May 2017

The epitaxial growth of ~250 μm thick 4H-SiC epilayers has been demanded for ultra-high-voltage power devices. We have attempted to improve the quality of thick epilayers. At the edge of wafer, stacking faults, epi-crown and interfacial dislocations could be well suppressed by controlling the distribution of growth rate. Investigation of carrier concentration depth profile revealed that increasing surface roughness increased the carrier concentration during thick epitaxial growth. Under N2-doped growth condition, memory effect by accumulation of by-products containing dopant element is also one of the reasons of the carrier concentration increasing during the growth.
Tuning Performance of Silicon Carbide Micro-Resonators
Authors: Cheung Rebecca , Wood Graham S. , Mastropaolo Enrico , Sviličić Boris
Published: May 2017

Silicon carbide microresonators have been designed, fabricated and tested. Three designs have been studied: cantilever, bridge and ring resonators. The devices have been actuated electrothermally and sensed piezoelectrically. The resonant frequency as well as the amount of frequency shift as a function of DC bias voltage for the three designs have been characterized electrically using two-port measurements. It has been found that the DC tuning sensitivities of the ring and bridge resonators (between 58,000 ppm/V and 62,000 ppm/V) are significantly higher than for the cantilever (240 ppm/V). Simulations have shown that a larger temperature change, hence a larger compressive stress induced in the SiC layer exists in the bridge design compared to the cantilever design as the DC bias voltage is increased. The higher DC tuning sensitivity for the bridge design could be a result of the combination of the location of the electrode thus causing higher thermally induced compressive stress as well as the clamped-clamped beam configuration.
Silicon Carbide Radiation Detectors for Medical Applications
Authors: Mohamed Nurul S. , Idris Muhammad I. , Wright Nick G. , Horsfall Alton B.
Published: May 2017

There is increasing interest in the development of radiation hard detector materials with the capability to discriminate within wide dose range and high radiation tolerance that are sensitive, and show a linear response. In this study, fabricated 4H-SiC Schottky diodes were exposed to dose rates ranging from 0.02 to 0.185 mGy/min to analyse the linearity and sensitivity at room temperature. High linearity response presented from the graph of current signal plotted versus dose rate which show enhancement of 104 in comparison to previous studies. The sensitivity measured at different bias voltages by exposing to 0.185 mGy/min dose rate show good reproducibility and stability of the current signal with time. Collected charge presented for all diodes exhibit linear behaviour of photon induced collected charge with the sensitivity between 1.40 to 8.38 x 105 nC/Gy for the 0.20 to 1 mGy absorbed dose range. Thus, these devices are ideally suited for the realisation of radiation detectors at moderate dose range.
Very High Sustainable Forward Current Densities on 4H-SiC p-n Junctions Formed by VLS Localized Epitaxy of Heavily Al-Doped p++ Emitters
Authors: Sejil Selsabil , Lalouat Loic , Lazar Mihai , Carole Davy , Brylinski Christian , Jomard François , Planson Dominique , Ferro Gabriel , Raynaud Christophe
Published: May 2017

This study deals with the electrical characterization of PiN diodes fabricated on a 4°off-axis 4H-SiC n+ substrate with a n- epilayer (1×1016 cm-3 / 10 µm). Optimized p++ epitaxial areas were grown by Vapour-Liquid-Solid (VLS) transport to form p+ emitters localized in etched wells with 1 µm depth. Incorporated Al level in the VLS p++ zones was checked by SIMS (Secondary Ion Mass Spectroscopy), and the doping level was found in the range of 1-3×1020 at.cm-3. Electrical characterizations were performed on these PiN diodes, with 800 nm deposit of aluminium as ohmic contact on p-type SiC. Electrical measurements show a bipolar behaviour, and very high sustainable forward current densities ≥ 3 kA.cm-2, preserving a low leakage current density in reverse bias. These measurements were obtained on structures without any passivation and no edge termination.
Localized Surface Plasmon on 6H SiC with Ag Nanoparticles
Authors: Wei Yi , Fadil Ahmed , Ou Hai Yan
Published: May 2017

Silver (Ag) nanoparticles (NPs) were deposited on the surface of bulk Nitrogen-Boron co-doped 6H silicon carbide (SiC), and the Ag NPs were observed to induce localized surface plasmons (LSP) resonances on the SiC substrate, which was expected to improve the internal quantum efficiency (IQE) of the emissions of the donor-acceptor pairs of the SiC substrate. Room-temperature measurements of photoluminescence (PL), transmittance and time-resolved photoluminescence (TRPL) were applied to characterize the LSP resonances. Through the finite-difference time-domain (FDTD) simulation of the LSP resonance of an Ag nanoparticle on the SiC substrate, it is predicted that when the diameter of the cross section on the xy plane of the Ag nanoparticle is greater than 225 nm, the LSP starts to enhance the PL intensity. With implementation of a 3rd order exponential decay fitting model to the TRPL results, it is found that the average minority carrier lifetime of the SiC substrate decreased.
Experimental Verification of a Self-Triggered Solid-State Circuit Breaker Based on a SiC BIFET
Authors: Albrecht Matthaeus , Huerner Andreas , Erlbacher Tobias , Bauer Anton J. , Frey Lothar
Published: May 2017

In this work, the feasibility of the Bipolar-Injection Field Effect-Transistor (BIFET) [5] in two different Dual Thyristor type circuits [4] for an application as solid-state circuit breaker (SSCB) is experimentally verified. The Dual Thyristor type circuits are assembled from discrete silicon JFETs and a silicon carbide BIFET and are electrically characterized at various temperatures. The current-voltage characteristic shows the expected regenerative self-triggered turn-off capability under over-currents and the option to control the turn-off current by a passive resistor network. The issue with the adverse positive temperature coefficient of the trigger-current can be solved by putting the SiC BIFET in a cascode arrangement with a silicon Dual Thyristor. In this configuration the SiC BIFET provides the high voltage blocking capability and the silicon Dual Thyristor with its negative temperature coefficient controls the trigger-current. Transient analyses of both circuits indicate fast switching times of less than 50 μs seconds. It is demonstrated for the first time, that the SiC BIFET, due to its normally-on behaviour, used in a Dual Thyristor type circuit is a promising concept for self-triggered fuses in high current and high voltage applications.
High Temperature Bipolar Master-Slave Comparator and Frequency Divider in 4H-SiC Technology
Authors: Hedayati Raheleh , Lanni Luigia , Shakir Muhammad , Salemi Arash , Zetterling Carl Mikael
Published: May 2017

This paper demonstrates a fully integrated master-slave emitter-coupled logic (ECL) comparator and a frequency divider implemented in 4H-SiC bipolar technology. The comparator consists of two latch stages, two level shifters and an output buffer stage. The circuits have been tested up to 500 °C. The single ended output swing of the comparator is -7.73 V at 25 °C and -7.63 V at 500 °C with a -15 V supply voltage. The comparator consumes 585 mW at 25 °C. The frequency divider consisting of two latches shows a relatively constant output voltage swing over the wide temperature range. The output voltage swing is 7.62 V at 25 °C and 7.32 V at 500 °C.
SiC Schottky Diode Rectifier Bridge Represented as Diffusion-Welded Stack
Authors: Korolkov Oleg , Kozlovski Vitalii V. , Lebedev Alexander A. , Land Raul , Sleptsuk Natalja , Toompuu Jana , Rang Toomas
Published: May 2017

We considered the prototype of a SiC Schottky diode Rectifier Bridge made on the basis of commercial SiC Schottky diodes by diffusion welding (DW). Vertical integration for four diode chips in combination with molybdenum electrodes can improve the overall weight and dimensions of the module performance and increase device durability to radiation exposure. Our DW prototype, in contrast to commercial bridges, completely preserved the initial characteristics after irradiation by electrons with an energy of 0.9 MeV and density of 3 x 1016 cm-2
Dislocation Revelation and Categorization for Thick Free-Standing GaN Substrates Grown by HVPE
Authors: Yao Yong Zhao , Ishikawa Yukari , Sugawara Yoshihiro , Yokoe Daisaku , Sudo Masaki , Okada N. , Tadatomo K.
Published: May 2017

Threading dislocations (TDs) in an HVPE-grown free-standing GaN substrate have been studied by means of etch pit method using molten KOH+Na2O2 solution, cathodoluminescence (CL) mapping and transmission electron microscopy (TEM). We have focused on the correlation between (1) Burgers vectors of TDs, (2) their appearances as dark spots in CL image, and (3) geometries of corresponding etch pits. Based on the above results, dislocation categorization for GaN by using etch pits or CL is discussed.
CVD Growth of Graphene on SiC (0001): Influence of Substrate Offcut
Authors: Dagher Roy , Jouault Benoit , Paillet Matthieu , Bayle Maxime , Nguyen Luan , Portail Marc , Zielinski Marcin , Chassagne Thierry , Cordier Yvon , Michon Adrien
Published: May 2017

In this study we report the growth of graphene on different silicon carbide substrates by chemical vapor deposition (CVD) in order to understand the influence of the substrate offcut on the graphene layers. For this purpose, graphene was grown on substrates with different offcuts, under hydrogen-argon atmosphere, and analyzed using AFM, LEED and Raman spectroscopy. We discuss the morphology and strain in graphene, and finally the ideal offcut for graphene growth.
Realization and Characterization of Carbonic Layers on 4H-SiC for Electrochemical Detections
Authors: Pezard Julien , Soulière Véronique , Lazar Mihai , Haddour Naoufel , Buret Francois , Raynaud Christophe , Planson Dominique
Published: May 2017

Carbon materials are considered building blocks for most of electrochemical sensors. Their biocompatibility allows their use as transducers for biosensors. Furthermore, they can be patterned, giving interest in all-inclusive bioelectrochemical detection devices. In particular, graphene, boron doped diamond, and pyrolyzed photoresist films are suitable for this kind of application, which would give the ability to use these working electrodes within a fully designed apparatus completed by counter and reference electrode. In this paper, a pioneer work is exposed on the synthesis of these materials for use as electrochemical sensors and as transducers for biodetection of acetylcholine by adsorption of acetylthiocholinesterase. The lowest limit of detection reaches 6.98 μM, sensitivity 5.91 μA/mM, and a linear range from 6.98 μM to 0.55 mM.
High Temperature Reliability Assessment and Degradation Analysis for Diamond Semiconductor Devices
Authors: Tanimoto Satoshi , Suzuki Tatsuhiro , Araki Sawa , Makino Toshiharu , Kato Hiromitsu , Ogura Masahiko , Yamasaki Satoshi
Published: May 2017

The long-term reliability of Schottky pn diodes (SPNDs) on diamond having widely used Ti/Pt/Au electrodes was investigated at 500°C in order to identify degradation phenomena at higher temperatures. A vital degradation event was observed after the passage of about 100 hours in that both forward and reverse currents were progressively reduced. AES depth profiling and X-STEM-EELS analyses revealed that this occurred because the Ti contact material changed to insulating (or semiconductive) TiO2, causing large series resistance.
Numerical Study of Energy Capability of Si/SiC LDMOSFETs
Authors: Chan Chun W. , Li Fan , Mawby Philip  Andrew , Gammon Peter Michael
Published: May 2017

A comparable study is made on the energy capability of 190 V LDMOSFETs in Si/SiC, SOI, PSOI and PSOSiC technology, using capacitive and inductive switching circuits established in SILVACO Mixed-mode simulators. The results show that the PSOSiC has a thermal advantage compared with other SOI structures under a 48-μs-power-pulse condition, but the Si/SiC device offers superior cooling and energy handling ability in all switching cases despite having a larger chip area.
Bulk β-Ga2O3 with (010) and (201) Surface Orientation: Schottky Contacts and Point Defects
Authors: Ingebrigtsen Mads E. , Vines Lasse , Alfieri Giovanni , Mihaila Andrei , Badstübner Uwe , Svensson Bengt Gunnar , Kuznetsov Andrej
Published: May 2017

Electrical properties of Schottky contacts of high work-function metals (Pd, Au, and Ni) on (010) and (201) oriented β-Ga2O3 were investigated. Current-voltage characteristics reveal that all the contacts exhibit high rectifying behavior with ideality factors as low as 1.04. However, the reverse leakage currents were lower in the (010) samples compared to the (201) ones. Thermal admittance spectroscopy confirms a main charge carrier level to be at ~0.15 eV below the conduction band edge (Ec). Secondary ion mass spectrometry indicates that Si may be responsible for this donor level. Deep level transient spectroscopy reveals four levels (E1-E4) in the upper part of the band gap, with the corresponding energy level positions at 0.56, 0.76, 1.01, and 1.48 eV below Ec.
Depth Profile of Doping Concentration in Thick (> 100 μm) and Low-Doped (< 4 × 1014 cm-3) 4H-SiC Epilayers
Authors: Fukada Keisuke , Ishibashi Naoto , Miyasaka Yoshihiko , Bandoh Akira , Momose Kenji , Osawa Hiroshi
Published: May 2017

The depth profiles of n-type doping concentration in thick (>100 μm) and low-doped (< 4 × 1014 cm-3) 4H-SiC epilayers grown by chemical vapor deposition (CVD) were investigated. The variation in doping concentration during epitaxial growth are considered to be caused by: (1) variation in gas flow due to parasitic deposition, (2) variation in precursor decomposition rate due to change in reactor temperature, (3) variation in dopant incorporation rate due to change in wafer temperature, and (4) variation in supply of background dopants. By controlling all these parameters, a constant depth profile in thick (> 100um) epilayers was realized.
A Study on 3C-SiC Carbonization on Misoriented Si Substrates: From Research to Production Scale Reactors
Authors: Bosi Matteo , Ferrari Claudio , Nilsson Daniel , Ward Peter J.
Published: May 2017

In this work we have studied the carbonization of 3C-SiC on misoriented Si substrates, using different thermal ramp rates and shapes. We observed that the heating rate (°C/sec) from carbonization temperature to film growth temperature plays a major role in controlling the void density. Moreover, void formation can be eliminated by the introduction of silane at different temperatures during the heating ramp. The studies were performed on a small research reactor and the results were successfully transferred to a production scale reactor, aimed to the production of 3C-SiC power devices manufactured on 100 and 150 mm Si substrates.
Susceptor Coating Materials Applicable for SiC Reactor Cleaning
Authors: Shioda Kohei , Habuka Hitoshi , Ito Hideki , Mitani Shinichi , Takahashi Yoshinao
Published: May 2017

In order to develop a cleaning process for the silicon carbide chemical vapor deposition reactor, the susceptor coating materials are developed for protecting the susceptor from the etching by chlorine trifluoride gas. The chlorine trifluoride gas does not give a serious damage to the pyrolitic carbon film at the temperatures lower than 480 °C, at which temperature the quick and practical reactor cleaning process is expected to be possible
Justiça de transição em sua gênese: a Alemanha pós-nazismo
Authors: Galindo Bruno
Published: May 2017

Este artigo tem por objetivo tratar das questões referentes à justiça de transição em seu início, analisando a primeira experiência histórica do fenômeno, a Alemanha pós-nazismo e o enfrentamento dos problemas oriundos do período em que esse país esteve sob o jugo do regime nazista. O trabalho envolve a análise de algumas importantes questões do constitucionalismo alemão dos períodos envolvidos e da ascensão e queda do referido regime. Tem por base metodológica as premissas da denominada teoria intercultural da constituição, bem como a classificação das constituições quanto à conformação do processo político, do constitucionalista alemão Karl Loewenstein, e a teoria dos regimes políticos híbridos da Professora espanhola Inmaculada Szmolka Vida. No trabalho, essas perspectivas teóricas se relacionam com os conceitos fundamentais da teoria da justiça de transição, algo provavelmente ainda não realizado em artigos temáticos a respeito. Ao fim, pretende-se traçar o alcance da justiça de transição na Alemanha em face da experiência do pós-nazismo, considerando as medidas e os objetivos propostos pela teoria da justiça de transição em seu atual estado da arte.
Conflitos entre regulações internas relativas à internet e o direito do comércio internacional: o papel da OMC perante o sistema de computação da nuvem
Authors: Rocha da Silva Alice , Soares Filipe Rocha Martins
Published: May 2017

A OMC tem um papel importante no aprimoramento da governança dos mecanismos de computação na plataforma de comercialização de bens e serviços, de modo específico a nuvem cibernética. Ao impor medidas como a censura, normas de proteção de dados privados ou a exigência de licenças prévias para o funcionamento de empresas, governos costumam fundamentar suas decisões no imperativo de garantir a segurança pública e assegurar a defesa nacional. Os Estados geralmente optam por limitar os fluxos internacionais de dados ao promoverem esse tipo de regulação sobre a internet. Ocorre que, ao fazê-lo, podem acabar por sufocar a rede, uma vez que a economia que se desenvolveu em torno dela é baseada na movimentação de informações. Ademais, não é raro que se promovam medidas protecionistas camufladas, o que afronta as regras do comércio internacional.
Edição Completa / Complete Issue
Authors: Varella Marcelo Dias , Monebhurrun [Editores] Nitish , Amaral Buani Christiani , Valim Magalhaes [Editores especiais] Bruno
Published: May 2017

Edição Completa
Air–water CO2 evasion from US East Coast estuaries
Authors: Laruelle Goulven Gildas , Goossens Nicolas , Arndt Sandra , Cai Wei-Jun , Regnier Pierre
Published: May 2017

Abstract. This study presents the first regional-scale assessment of estuarine CO2 evasion along the US East Coast (25–45° N). The focus is on 42 tidal estuaries, which together drain a catchment of 697 000 km2 or 76 % of the total area within this latitudinal band. The approach is based on the Carbon–Generic Estuary Model (C-GEM) that allows the simulation of hydrodynamics, transport, and biogeochemistry for a wide range of estuarine systems using readily available geometric parameters and global databases of seasonal climatic, hydraulic, and riverine biogeochemical information. Our simulations, performed using conditions representative of the year 2000, suggest that, together, US East Coast estuaries emit 1.9 Tg C yr−1 in the form of CO2, which corresponds to about 40 % of the carbon inputs from rivers, marshes, and mangroves. Carbon removal within estuaries results from a combination of physical (outgassing of supersaturated riverine waters) and biogeochemical processes (net heterotrophy and nitrification). The CO2 evasion and its underlying drivers show important variations across individual systems, but reveal a clear latitudinal pattern characterized by a decrease in the relative importance of physical over biogeochemical processes along a north–south gradient. Finally, the results reveal that the ratio of estuarine surface area to the river discharge, S∕Q (which has a scale of per meter discharged water per year), could be used as a predictor of the estuarine carbon processing in future regional- and global-scale assessments.
δ11B as monitor of calcification site pH in marine calcifying
organisms
Authors: Sutton Jill N. , Liu Yi-Wei , Ries Justin B. , Guillermic Maxence , Ponzevera Emmanuel , Eagle Robert A.
Published: May 2017

Abstract. The isotope composition of boron (B) in marine biogenic carbonates has been predominantly studied as a proxy for monitoring past changes in seawater pH and carbonate chemistry. In order to derive seawater pH from boron isotope ratio data, a number of assumptions related to chemical kinetics and themodynamic isotope exchange reactions are necessary. Furthermore, the boron isotope composition (δ11B) of biogenic carbonates (δ11BCaCO3) is assumed to reflect the δ11B of dissolved borate (B(OH)4−) in seawater. Here we report the development of methodology for measuring the δ11B in biogenic carbonate samples at the multi-collector inductively coupled mass spectrometry facility at Ifremer (Plouzané, France) and the evaluation of δ11BCaCO3 in a diverse range of marine calcifying organisms. We evaluated the δ11BCaCO3 of 6 species of marine calcifiers (a temperate coral, Oculina arbuscula; a coralline red alga, Neogoniolithion sp.; a tropical urchin, Eucidaris tribuloides; a temperate urchin, Arbacia punctulata; a serpulid worm, Hydroides crucigera; and an American oyster, Crassostrea virginica) that were reared for 60 days in isothermal seawater (25 °C) equilibrated with an atmospheric pCO2 of ca. 409 μatm. We observe large inter-species variability in δ11BCaCO3 (ca. 20 ‰) and significant discrepancies between measured δ11BCaCO3 and δ11BCaCO3 expected from established relationships between δ11BCaCO3 and seawater pH. We discuss these results in the context of various proposed mechanisms of biocalcification, including the potential dominant role that internal calcifying site pH plays in regulating CaCO3 saturation state and borate δ11B at the site of calcification and, thus, the δ11B composition of calcifers’ shells and skeletons.