bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Growth Conditions on Carrier Lifetime in N-Type 4H-SiC Epitaxial Layers
Authors: Lilja Louise , Hassan Jawad , Booker I.D. , Bergman Peder , Janzén Erik
Published: May 2012

Carrier lifetime has been studied as a function of C/Si ratio and growth rate during epitaxial growth of n-type 4H-SiC using horizontal hot-wall CVD. Effort has been put on keeping all growth parameters constant with the exception of the parameter that is intended to vary. The carrier lifetime is found to decrease with increasing growth rate and the highest carrier lifetime is found for a C/Si ratio of 1. The surface roughness was correlated with epitaxial growth conditions with AFM analysis.
Study of the Lateral Growth by VLS Mechanism Using Al-Based Melts on Patterned SiС Substrate
Authors: Lorenzzi Jean , Esteve Romain , Lazar Mihai , Tournier Dominique , Carole Davy , Ferro Gabriel
Published: May 2012

In this work we report on SiC epitaxial growth by vapour-liquid-solid (VLS) mechanism on on-axis 4H-SiC(0001) substrates which were previously patterned to form mesa structures. The liquid phase was set to Al70Si30. At 1100°C, it led to very high homoepitaxial lateral growth (140 µm/h) with pronounced spiral growth and in plane anisotropy of growth rate. Upon temperature increase to 1200 °C, this spiral growth was suppressed and the lateral growth was further increased up to 180 µm/h. The in-plane versus out-of-plane anisotropy of growth rate was found to be as high as 60 at this temperature and 46 at 1100°C.
Freestanding 3C-SiC Grown by Sublimation Epitaxy Using 3C-SiC Templates on Silicon
Authors: Hens Philip , Müller Julian , Wagner Günter , Liljedahl Rickard , Yakimova Rositza , Spiecker Erdmann , Wellmann Peter J. , Syväjärvi Mikael
Published: May 2012

In this work a new approach for the production of freestanding cubic silicon carbide (3C SiC) in (001) orientation is presented which is based on the combination of chemical vapor deposition (CVD) and the fast sublimation growth process (FSGP). Fast homoepitaxial growth of 3C SiC using sublimation epitaxy on a template created by CVD growth on silicon substrates allows to obtain thick freestanding material with low defect densities. Using standard silicon wafers as substrate material permits a cost efficient process and the applying of wafers with different orientations. The (001) orientation used in this work will potentially allow further heteroepitaxial growth of other cubic semiconductors, like e.g. gallium nitride (GaN).
Effect of Propane on Low Temperature Growth of 3C-SiC Film on Si (111) by Plasma Assisted CVD
Authors: Shimizu Hideki , Watanabe Takashi
Published: May 2012

To demonstrate the formation of 3C-SiC film on Si (111) at low substrate temperature, the effects of C3H8 on the crystalline quality of the 3C-SiC films on Si (111) have been investigated by changing the flow rate of C3H8 at the substrate temperature of 950 °C. The crystalline quality has been investigated by transmission electron microscope and X-ray diffraction. 3C-SiC is epitaxially grown on Si(111) and the 3C-SiC films are in either near single crystalline or highly oriented form with stacking faults and twin. It is expected that the film with good crystalline quality may grow at around 2.5 in the ratio of the flow rate of C3H8 to SiH4 and any microstructures of 3C-SiC films on Si (111) can be controlled by accurately controlling the ratio of C/Si.
On Stabilization of 3C-SiC Using Low Off-Axis 6H-SiC Substrates
Authors: Jokubavicius Valdas , Lundqvist Björn , Hens Philip , Liljedahl Rickard , Yakimova Rositza , Kamiyama Satoshi , Syväjärvi Mikael
Published: May 2012

Heteroepitaxial growth of 3C-SiC on 0.8 and 1.2 degree off-oriented 6H-SiC substrates was studied using a sublimation growth process. The 3C-SiC layers were grown at high growth rates with layer thickness up to 300 µm. The formation and the quality of 3C-SiC are influenced by the off-orientation of the substrate, the growth temperature (studied temperature range from 1750 °C to 1850°C), and the growth ambient (vacuum at 5*10-5 mbar and nitrogen at 5*10-1 mbar). The largest domains of 3C-SiC and the lowest number of double positioning boundaries were grown using nitrogen ambient and the highest growth temperature. The combined use of low off-axis substrate and high growth rate is a potential method to obtain material with bulk properties.
Electronic Configuration of Tungsten in 4H-, 6H-, and 15R-SiC
Authors: Gällström Andreas , Magnusson Björn , Beyer Franziska Christine , Gali Adam , Son Nguyen Tien , Leone Stefano , Ivanov Ivan G. , Henry Anne , Hemmingsson Carl G. , Janzén Erik
Published: May 2012

A commonly observed unidentified photoluminescence center in SiC is UD-1. In this report, the UD-1 center is identified to be tungsten related. The identification is based on (i) a W-doping study, the confirmation of W in the samples was made using deep level transient spectroscopy (DLTS), (ii) the optical activation energy of the absorption of UD-1 in weakly n-type samples corresponds to the activation energy of the deep tungsten center observed using DLTS. The tungsten-related optical centers are reported in 4H-, 6H-, and 15R-SiC. Further, a crystal field model for a tungsten atom occupying a Si-site is suggested. This crystal field model is in agreement with the experimental data available: polarization, temperature dependence and magnetic field splitting.
Identification of Niobium in 4H-SiC by EPR and Ab Initio Studies
Authors: Son Nguyen Tien , Ivády Viktor , Gali Adam , Gällström Andreas , Leone Stefano , Kordina Olof , Janzén Erik
Published: May 2012

In unintentionally Nb-doped 4H-SiC grown by high-temperature chemical vapor deposition (HTCVD), an electron paramagnetic resonance (EPR) center with C1h symmetry and an electron spin S=1/2 was observed. The spectrum shows a hyperfine structure consisting of ten equal-intensity hyperfine (hf) lines which is identified as due to the hf interaction between the electron spin and the nuclear spin of 93Nb. An additional hf structure due to the interaction with two equivalent Si neighbors was also observed. Ab initio supercell calculations of Nb in 4H-SiC suggest that Nb may form complex with a C-vacancy (VC) resulting in an asymmetric split-vacancy (ASV) defect, NbSi-VC. Combining results from EPR and supercell calculations, we assign the observed Nb-related EPR center to the hexagonal-hexagonal configuration of the AVS defect in the neutral charge state, (NbSi-VC)0.
Chlorine in SiC: Experiment and Theory
Authors: Alfieri Giovanni , Kimoto Tsunenobu
Published: May 2012

An annealing study, in the 100-1400 C temperature range ,was carried out on Cl-implanted n- or p-type 4H-SiC epilayers. The electrical characterization of the epilayers shows the rise of several deep levels and the role of Cl, on both carrier concentration and defects' microscopic structure, is discussed in the light of theoretical results obtained by density functional calculations performed on a 64-atom cubic SiC supercell.
On the Formation of Intrinsic Defects in 4H-SiC by High Temperature Annealing Steps
Authors: Zippelius Bernd , Suda Jun , Kimoto Tsunenobu
Published: May 2012

In this paper the impact of high temperature annealing on the formation of intrinsic defects in 4H-SiC such as Z1/2 and EH6/7 was examined. Therefore, three epitaxial layers with various initial concentrations of the Z1/2- and EH6/7-centers (1011 – 1013 cm-3) were investigated. It turns out that depending on the initial defect concentration the high temperature annealing leads to a monotone increase of the Z1/2- and EH6/7-concentration in a temperature range from 1600 to 1750°C. For a defined temperature above these values, the resulting defect concentration is independent of the sample’s initial values. Beside the growth conditions themselves such as C/Si ratio the thermal post-growth processing has a severe impact on the carrier lifetime which must be taken into account during device fabrication.
Analysis of Growth Velocity of SiС Growth by the Physical Vapor Transport Method
Authors: Kakimoto Koichi , Gao Bing , Shiramomo Takuya , Nakano Satoshi , Nishizawa Shin Ichi
Published: May 2012

Crystal growth velocity of SiC in a process of physical vapor transport was studied on the basis of numerical calculation including compressible effect, convection and buoyancy effects, flow coupling between argon gas and species, and the Stefan effect. Calculation in 2D configuration was performed to clarify the effect of pressure on growth velocity. The results revealed that the origin of diffusion resistance reported so far was the effect of convection of argon gas and chemical species.
Z1/2- and EH6-Center in 4H-SiC: Not Identical Defects ?
Authors: Zippelius Bernd , Glas Alexander , Weber Heiko B. , Pensl Gerhard , Kimoto Tsunenobu , Krieger M.
Published: May 2012

Deep Level Transient Spectroscopy (DLTS) and Double-correlated DLTS (DDLTS) measurements have been conducted on Schottky contacts fabricated on n-type 4H-SiC epilayers using different contact metals in order to separate the EH6- and EH7-centers, which usually appear as a broad double peak in DLTS spectra. The activation energy of EH6 (EC - ET(EH6) = 1.203 eV) turns out to be independent of the electric field. As a consequence, EH6 is acceptor-like according to the missing Poole-Frenkel effect. Therefore, it can be excluded that the EH6-center and the prominent acceptor-like Z1/2-center belong to different charge states of the same microscopic defect as theoretically suggested. It is proposed that EH6 is a complex containing a carbon vacancy and another component available at high concentrations. The activation energy of EH7 (EC - ET(EH7) = 1.58 eV) has been evaluated indirectly by fitting the DLTS spectra of the EH6/7 double peak taking the previously determined parameters of EH6 into account.
Effects of Sacrifice Oxidation on Characterization of Defects in High-Purity Semi-Insulating 4H-SiC by Discharge Current Transient Spectroscopy
Authors: Nishikawa Seiji , Okada Ryota , Matsuura Hideharu
Published: May 2012

To determine the energy levels of intrinsic defects in high-purity semi-insulating 4H-SiC, we apply discharge current transient spectroscopy (DCTS) that is a graphical peak analysis method based on the transient reverse current of a Schottky barrier diode, because transient capacitance methods such as deep level transient spectroscopy and isothermal capacitance transient spectroscopy are feasible only in low-resistivity semiconductors. The reverse current consists the reverse current through the balk and the surface leakage current of the diode. It is elucidated that the sacrifice oxidation could dramatically reduce the surface currents of diodes in the case of high-purity semi-insulating 4H-SiC, suggesting that the densities and emission rates of traps in the bulk of the SiC can be determined from the transient reverse current.
Investigation of Additional States in the Silicon Carbide Surface after Diffusion Welding
Authors: Mizsei János , Korolkov Oleg , Sleptsuk Natalja , Toompuu Jana , Rang Toomas
Published: May 2012

This paper is a summary of the experimental study of deep levels in a SiC crystal lattice caused by diffusion welding (DW). Investigations were carried out by DLTS and Kelvin Probe methods. Investigations revealed that DLTS method is not applicable for identification of surface states. Research conducted by the Kelvin Probe method has shown an increase in the density of surface states after the diffusion welding from 2x1015 cm-2 to 3.5x1016 cm-2.
Long Carrier Lifetimes in n-Type 4H-SiC Epilayers
Authors: Klein Paul B.
Published: May 2012

Recent advances in preparing n-type 4H-SiC with long carrier lifetimes have greatly enhanced the possibility of realizing commercially available, very high voltage and high power solid state switching diodes. For the range > several kV, vertical bipolar structures are required with drift layers exhibiting carrier lifetimes ≥ several µsec. Recently, low-doped epilayers with carrier lifetimes in excess of this have been demonstrated, thus approaching a goal that has been pursued for over a decade. Historically, the short lifetimes in early epitaxial layers (a few hundred nsec) were eventually identified with the Vc-related Z1/2 lifetime killer. Current strategies to minimize this defect are an essential ingredient in the procedure for obtaining long-lifetime material. In order to optimize the attainable lifetimes, it has been shown that in addition to low Z1/2 levels, very thick layers are required to minimize the effects of recombination in the substrate and surface passivation is also necessary to minimize surface recombination (S < 1000 cm/sec).
Radial Variation of Measured Carrier Lifetimes in Epitaxial Layers Grown with Wafer Rotation
Authors: Bergman Peder , Booker I.D. , Lilja Louise , Hassan Jawad , Janzén Erik
Published: May 2012

In this report we present homoepitaxial growth of 4H-SiC on the Si-face of nominally on-axis substrates with diameter up to 100 mm in a hot-wall chemical vapor deposition reactor. A comparatively low carrier lifetime has been observed in these layers. Also, local variations in carrier lifetime are different from standard off-cut epilayers. The properties of layers were studied with more focus on charge carrier lifetime and its correlation with starting growth conditions, in-homogeneous surface morphology and different growth mechanisms.
Effect of Nitrogen Doping on the Growth of 4H Polytype on the 6H-SiC Seed by PVT Method
Authors: Tymicki Emil , Grasza Krzysztof , Racka Katarzyna , Łukasiewicz Tadeusz , Piersa Miroslaw , Kościewicz Kinga , Teklińska Dominika , Diduszko Ryszard , Skupiński Paweł , Jakieła Rafał , Krupka Jerzy
Published: May 2012

In this work results of nitrogen doping in the amount of 0 vol.%, 3 vol.% and 10 vol.% on the growth of the 4H polytype on the 6H-SiC seed are presented. SiC crystals grown by PVT method on the (000-1) C-face of 6H seeds using the open seed backside design have been investigated. Structural and electrical properties of the crystals were studied by different experimental methods.
Correlation between Strain and Excess Carrier Lifetime in a 3C-SiC Wafer
Authors: Yoshida Atsushi , Kato Masashi , Ichimura Masaya
Published: May 2012

We obtained excess carrier lifetime maps by the microwave photoconductivity decay (µ-PCD) method in a free-standing n-type 3C-SiC wafer, and then we compared the lifetime maps with distributions of strains and defects observed by the optical microscopy and the Raman spectroscopy. We found that the excess carrier lifetimes are short in a strained region in 3C-SiC, which indicates that structural defects exist around a strained region.
Carrier Diffusivity in Highly Excited Bulk SiC, GaN, and Diamond Crystals by Optical Probes
Authors: Jarašiūnas Kęstutis , Ščajev Patrik , Malinauskas Tadas , Kato Masashi , Ivakin Evgenii , Nesladek Milos , Haenen Ken , Özgür Ümit , Morkoç Hadis
Published: May 2012

Optical monitoring of diffusivity in wide bandgap semiconductors was performed by using a picosecond light-induced transient grating technique. The bandgap renormalization and carrier-carrier scattering manifested itself at room temperature as two-fold decrease of the ambipolar diffusion coefficient Da in cubic SiC and 5-fold decrease of Da in diamond at excess carrier density N > 1017 cm-3, while for GaN the impact was observed only at T 19 cm-3, the plasma degeneracy led to enhanced Da values in SiC and GaN and compensated the diffusivity decrease in diamond.
Critical Conditions of Misfit Dislocation Formation in 4H-SiC Epilayers
Authors: Zhang Xuan , Miyazawa Tetsuya , Tsuchida Hidekazu
Published: May 2012

Thermal annealing experiments were performed to determine the critical conditions of misfit dislocation formation in 4H-SiC epilayers in a temperature range of 1400-1800 °C. Misfit dislocations were observed to form at a given annealing temperature if the temperature gradient across the epi-wafer exceeded a critical value. It was also found that two types of interfacial dislocations could form under different stress conditions. Their formation mechanisms are discussed.
X-Ray Three-Dimensional Topography Imaging of Basal-Plane and Threading-Edge Dislocations in 4H-SiC
Authors: Tanuma Ryohei , Mori Daisuke , Kamata Isaho , Tsuchida Hidekazu
Published: May 2012

This paper demonstrates the X-ray three-dimensional (3D) topography of basal-plane dislocations (BPDs) and threading edge dislocations (TEDs) in 4H-SiC for the first time. Stereographic topographs are obtained for BPDs and TEDs, showing the propagation of BPDs from a substrate to an epilayer and the conversion of BPDs into TEDs near the epilayer/substrate interface. Strain analysis is also demonstrated for a TED, providing the image of strains in the order of ±10-5. It is verified that the 3D topography is successfully applicable to BPDs and TEDs.
Lateral Growth Expansion of 4H/6H-SiС M-Plane Pseudo Fiber Crystals by Hot Wall CVD Epitaxy
Authors: Trunek Andrew J. , Neudeck Philip G. , Woodworth Andrew A. , Powell J. Anthony , Spry David J. , Raghothamachar Balaji , Dudley Michael
Published: May 2012

Lateral expansion of small mixed polytype 4H/6H-SiC and 6H-SiC slivers were realized by hot wall chemical vapor deposition (HWCVD). Small slivers cut from m-oriented (11 ̅00) SiC boule slices containing regions of 4H and 6H-SiC or just single polytype 6H-SiC were exposed to HWCVD conditions using standard silane/propane chemistry for a period of up to eight hours. The slivers exhibited approximately 1500 μm (1.5 mm) of total lateral expansion. Initial analysis by synchrotron white beam x-ray topography (SWBXT) confirms, that the lateral growth was homoepitaxial, matching the polytype of the respective underlying region of the seed sliver.
Synchrotron X-Ray Topography Studies of the Propagation and Post-Growth Mutual Interaction of Threading Growth Dislocations with C-Component of Burgers Vector in PVT-Grown 4H-SiC
Authors: Wu Fang Zhen , Wang Huan Huan , Byrapa Sha Yan , Raghothamachar Balaji , Dudley Michael , Sanchez Edward , Hansen Darren M. , Drachev Roman , Mueller Stephan G. , Loboda Mark J.
Published: May 2012

Synchrotron White Beam X-ray Topography (SWBXT) imaging of wafers cut parallel to the growth axis from 4H-SiC boules grown using Physical Vapor Transport has enabled visualization of the evolution of the defect microstructure. Here we present observations of the propagation and post-growth mutual interaction of threading growth dislocations with c-component of Burgers vector. Detailed contrast extinction studies reveal the presence of two types of such dislocations: pure c-axis screw dislocations and those with Burgers Vector n1c+n2a, where n1 is equal to 1 and n2 is equal to 1 or 2. In addition, observations of dislocation propagation show that some of the threading dislocations with c-component of Burgers adopt a curved, slightly helical morphology which can drive the dislocations from adjacent nucleation sites together enabling them to respond to the inter-dislocation forces and react. Since all of the dislocations exhibiting such helical configurations have significant screw component, and in view of the fact that such dislocations are typically not observed to glide, it is believed that such morphologies result in large part from the interaction of a non-equilibrium concentration of vacancies with the originally approximately straight dislocation cores during post-growth cooling. Such interactions can lead to complete or partial Burgers vector annihilation. Among the reactions observed are: (a) the reaction between opposite-sign threading screw dislocations with Burgers vectors c and –c wherein some segments annihilate leaving others in the form of trails of stranded loops comprising closed dislocation dipoles; (b) the reaction between threading dislocations with Burgers vectors of -c+a and c+a wherein the opposite c-components annihilate leaving behind the two a-components; (c) the similar reaction between threading dislocations with Burgers vectors of -c and c+a leaving behind the a-component.
Complex Behavior of Threading Dislocations Observed in PVT-Grown 4H-SiC Single Crystals
Authors: Katsuno Masakazu , Fujimoto Tatsuo , Yashiro Hirokatsu , Tsuge Hiroshi , Sato Shinya , Hirano Hosei , Yano Takayuki , Ohashi Wataru
Published: May 2012

Structures and propagating behaviors of threading dislocations (TDs) in PVT-grown 4H-SiC single crystals were both investigated using Synchrotron monochromatic X-ray topography. Comparative studies by examining images obtained for the crystals with different diffraction geometries of (0004) and (11-20) of 4H-SiC revealed that a large amount of TDs are likely to be mixed in character, i.e., dislocations with Burgers vector components of both <0004> and <11-20>. Closer observations of topography images has revealed that, although TDs lie largely along the c-axis direction, some of the TDs show quite a complex propagating behavior: not extending in a straight line but meandering along the growth direction.
Correlation between Surface Morphological Defects and Crystallographic Defects in SiC
Authors: Hatakeyama Tetsuo , Ichinoseki Kyoichi , Yamaguchi Hiroshi , Sugiyama N. , Matsuhata Hirofumi
Published: May 2012

The origins of certain types of micrometer-scale surface morphological defects on SiC epitaxial layers are clarified using X-ray topography. Two types of surface morphological defects are commonly observed on Si- and C-face epitaxial layers. Relatively large pits (around 4μm×2μm) originate from threading screw dislocations (TSDs). Relatively small pits (around 1.5μm×1μm) originate from threading edge dislocations (TEDs). The shapes and depths of these surface morphological pits depend on the fabrication history of the epitaxial wafers.
Synthesis and Purification of Silicon Carbide Powders for Crystal Growth
Authors: Hsiao Ta Ching , Tsao Sheng
Published: May 2012

Silicon carbide powders were prepared in a vacuum induction melting furnace (VIM). Silica and silicon were used as sources of silicon, and graphite powder was used a source of carbon. Pressures of 0.1 and 0.01 atm were selected as the operation conditions, and different silicon carbide powders were prepared. Free carbon and remnant silica were removed by high-temperature baking in air and acid leaching. Low-pressure powders show better crystallinity; moreover, free carbon and silica were rarely found in the product after baking and leaching. The low-pressure grains were prismatic whereas the high-pressure grains were porous. This shows that pressure is a critical parameter in silicon carbide formation, and low-pressure makes the low-temperature synthesis of silicon carbide feasible. Glow discharge mass spectra were used to analyze the impurity content in silicon carbide powders. After baking and leaching, the purity is increased from 3N5 (99.95 wt.%) to 4N5 (99.995 wt.%). Further purification procedures will be combined to meet the quality requirements for crystal growth.
Critical Density of Nanoscale Pits for Suppressing Variability in Leakage Current of a SiC Schottky Barrier Diode
Authors: Ishikawa Tsuyoshi , Katsuno T. , Watanabe Y. , Fujiwara H. , Endo T.
Published: May 2012

We investigate the influence of SiC surface morphology on increase and variability in reverse leakage current of SiC Schottky barrier diodes using device simulation. It is found that etch pits with only a few tens of nm in depth has a large influence on leakage current and is also shown that leakage current is sensitive to both etch pit shape and density. From these results, we suggest the critical density of nanoscale pit, which is suppressing the variability of leakage current, at various drift layer thickness tdrift and doping concentration Ndrift.
Density and Behavior of Etch Pits on C-Face 4H-SiC Surface Produced by CIF3 Gas
Authors: Habuka Hitoshi , Furukawa Kazuchika , Kanai Toshimitsu , Kato Tomohisa
Published: May 2012

The etch pit density produced on the C-face 4H-SiC substrate using chlorine trifluoride gas at various temperatures was evaluated. Because the etch pit density formed at the substrate temperature of 713 K showed the comparable value to the current dislocation level of the Si-face 4H-SiC, the etch pit density obtained by this technique is considered to have a relationship with the crystal quality.
Ultraviolet Photoluminescence Imaging of Stacking Fault Contraction in 4H-SiC Epitaxial Layers
Authors: Mahadik Nadeemullah A. , Stahlbush Robert E. , Caldwell Joshua D. , Hobart Karl D.
Published: May 2012

Shockley stacking fault (SSF) contraction in 4H-SiC was investigated, in-situ, under varying temperature and ultraviolet (UV) intensity. Contraction of single SSFs at room temperature was observed for the first time under low power UV excitation of 0.04 W/cm2. At temperatures above 150 °C, complete SSF contraction occurred for UV power at 0.2 W/cm2. In contrast to expansion, SSF contraction occurred in discrete jumps between pinning sites along existing C-core partials. Luminescence from the pinning sites suggest they may be local concentrations of point defects. Additionally, a change in the line direction of the Si-core partials by ~25o off the direction was observed.
Room Temperature Photoluminescence from 4H-SiC Epilayers: Non-Destructive Estimation of In-Grown Stacking Fault Density
Authors: Omar Sabih U. , Song Hai Zheng , Sudarshan Tangali S. , Chandrashekhar M.V.S.
Published: May 2012

Room temperature photoluminescence was obtained by UV excitation of homoepitaxially grown 4H-SiC thin films. A broad band emission from boron deep levels centered at 517nm was observed along with the band-edge emission of 4H-SiC at 391 nm. The wavelength of the excitation was varied and the change in the relative intensity of the two emission peaks was observed. The variation of the relative intensity was correlated with the in-grown stacking fault density in the epilayer. A physical model was developed to explain the correlation in terms of carrier diffusion length. For epilayers with very high density of in-grown stacking faults, a sharp emission was observed at 480nm.
Bulk and Surface Effects on the Polytype Stability in SiC Crystals
Authors: Mercier Frédéric , Nishizawa Shin Ichi
Published: May 2012

We investigated with ab initio calculations the 3C-, 6H-, 4H- and 2H-SiC polytypes. We discuss the geometry and the energetics of bulk and surface relaxed structures ((0001) Si face and the (000-1) C face surfaces). The polytype stability is discussed regarding the bulk and surface effects.
Interaction of 6H-Type Stacking Faults with Threading Screw Dislocations in PVT-Grown 4H-SiC Single Crystals
Authors: Sato Shinya , Fujimoto T. , Tsuge H. , Katsuno M. , Ohashi W.
Published: May 2012

6H-type stacking faults (SFs) observed in PVT-grown 4H-SiC ingle crystals were investigated using Photoluminescence (PL) microscopy at room temperature. Structural analyses using high resolution X-ray topography have revealed that there exist no (n=4, 8) component in Burger’s vectors of the 6H-type SFs we observed, strongly suggesting that the 6H-type SFs are constructed either by insertions of very thin 6H-type foreign polytype inclusions or by successive repetitions of Shockley-type in-plane glides.
Definitive Identification of an Important 4H SiC MOSFET Interface/Near Interface Trap
Authors: Cochrane Corey J. , Lenahan Patrick M. , Lelis Aivars J.
Published: May 2012

We utilize electrically detected magnetic resonance (EDMR) via spin dependent recombination (SDR) to provide a definitive identification of an interface/near interface defect present in a wide variety of 4H SiC/SiO2 metal oxide semiconducting field effect transistors (MOSFETs).
Comparative Study of Electrical and Microstructural Properties of 4H-SiC MOSFETs
Authors: Strenger Christian , Haeublein Volker , Erlbacher Tobias , Bauer Anton J. , Ryssel Heiner , Beltran Ana Maria , Schamm-Chardon Sylvie , Mortet Vincent , Bedel-Pereira Eléna , Lefebvre Mathieu , Cristiano Fuccio
Published: May 2012

N-channel MOSFETs were manufactured on p-type and on p-implanted, n-type 4H-SiC substrates. The electron mobility in the inversion channel was measured to be correlated with the structural and chemical properties determined by transmission electron microscopy. With regard to what was previously discussed in the literature, interfacial layer formation and carbon distribution across the SiC/SiO2 interface were considered in relation with the measured Hall electron mobility.
Oxidation-Induced Epilayer Carbon Di-Interstitials as a Major Cause of Endemically Poor Mobilities in 4H-SiC/SiO2 Structures
Authors: Shen Xiao , Pantelides Sokrates T.
Published: May 2012

The defects at the interface and in the oxide have been considered as the sources of mobility degradation at the SiC/SiO2 interface as in the case of Si/SiO2 system. By examining available experimental and theoretical results and performing new calculations, we show that thermal oxidation creates immobile carbon di-interstitial defects inside the semiconductor substrate, which are a major cause of the poor mobility in SiC/SiO2 structures.
Crystallinity Evaluation of 4H-SiC Single Crystal Grown by Solution Growth Technique Using Si-Ti-C Solution
Authors: Kamei Kazuhito , Kusunoki Kazuhiko , Yashiro Nobuyuki , Okada Nobuhiro , Moriguchi Koji , Daikoku H. , Kado M. , Suzuki H. , Sakamoto H. , Bessho T.
Published: May 2012

Crystallinity of 4H-SiC bulk crystal obtained by solution growth technique was characterized mainly by KOH etching of the off-ground and serially ground specimen. Marked reduction of basal plane dislocation, threading edge and screw dislocations during the growth of on-axis crystal was confirmed. Cross-sectional TEM observation revealed the rapid reduction behavior of threading dislocations microscopically. AFM observation of as-grown morphology showed that screw dislocation dipoles is related to the reduction of threading screw dislocations and single domain formation, which is essential for establishing the high crystallinity.
Total Near Interface Trap Density Calculation of 4H-SiC/SiO2 Structures before and after Nitrogen Passivation
Authors: Salemi Shahrzad , Akturk Akin , Potbhare Siddharth , Lelis Aivars J. , Goldsman Neil
Published: May 2012

We compare the effect of hydrogen, nitrogen, and phosphorous passivation on total near interface trap density and mobility of 4H(0001)-SiC/SiO2 structure. The results show that nitrogen and phosphorous passivation decrease total near interface trap density by pushing the energy levels of interface traps away from the conduction band. The density of states (DOS), including interface states (Dit), are calculated for several 4H(0001)-SiC/SiO2 structures using density functional theory (DFT).
Peak Degradation of Heavy-Ion Induced Transient Currents in 6H-SiC MOS Capacitors
Authors: Makino Takahiro , Iwamoto Naoya , Onoda Shinobu , Ohshima Takeshi , Kojima Kazutoshi , Nozaki Shinji
Published: May 2012

Peak value degradation of heavy-ion induced transient currents in Metal-Oxide-Semiconductor (MOS) capacitors fabricated on n-type and p-type 6H-SiC was observed. The capacitances of MOS capacitors measured during the ion irradiation suggest that the depletion layer width decreased with increasing number of incident ions and was saturated. Since the number of incident ions obtained at the peak current saturation corresponded to that at the saturation of the capacitance, the decrease in peak current can be interpreted in terms of the decrease in the depletion layer width.
Low Frequency Noise in 4H-SiC Lateral JFET Structures
Authors: Chan Hua Khee , Stevens Rupert C. , Goss Jonathan P. , Wright Nicholas G. , Horsfall Alton B.
Published: May 2012

Low frequency noise on 4H-SiC low-level signal-lateral JFETs was systematically investigated. In contrast to previous studies, which are based upon high power vertical structures, this work investigates the low-frequency noise behaviour of low-level signal-lateral devices which are more relevant to the realisation of small signal amplifiers.The JFETs studied share an identical cross section, with different gate lengths and widths. For high temperature operation between 300K and 700K at VGS = 0V, the Normalised Power Spectral Density (NPSD) of the JFETs is proportional to ƒ-1. The NPSD increases monotonically with temperature until a critical temperature, where it starts to decline. Two unique noise origins, fluctuation from bulk and SiO2-SiC interface traps were observed across all the devices investigated. Low frequency noise for devices with a 50μm gate width is localised at the SiO2-SiC interface, whereas for wider devices the noise is seen to be of bulk/substrate origin, which follows Hooge’s model.
High Resolution X-Ray Diffraction (HRXRD) Studies of the Initial Stages of PVT-Growth of 4H-SiC Crystals
Authors: Ohtani Noboru , Katsuno Masakazu , Fujimoto T. , Sato S. , Tsuge Hiroshi , Ohashi Wataru , Matsuhata Hirofumi , Kitabatake Makoto
Published: May 2012

Defect formation during the early stages of physical vapor transport (PVT) growth of 4H-SiC was investigated using high resolution x-ray diffraction (HRXRD). Characteristic lattice bending behaviors were revealed in the nearby seed crystal regions of grown crystals. The lattice bending was localized in close proximity to the seed/grown crystal interface, and the (0001) basal planes bended convexly toward the growth direction, indicative of the insertion of extra-half planes pointing toward the growth direction during the initial stages of crystal growth. This paper discusses the possible mechanisms of the observed lattice bending and sheds light on the defect formation processes during PVT-growth of 4H-SiC single crystals.
On the Stability of 3C-SiC Single Crystals at High Temperatures
Authors: Dompoint Deborah , Galben-Sandulache Irina G. , Boulle Alexandre , Chaussende Didier , Eyidi Dominique , Demenet Jean Luc , Beaufort Marie France , Rabier Jacques
Published: May 2012

The 3C-6H polytypic transition in 3C-SiC single crystals is studied by means of diffuse X-ray scattering (DXS) coupled with transmission electron microscopy (TEM). TEM reveals that the partially transformed SiC crystals contain regions of significantly transformed SiC (characterized by a high density of stacking faults) co-existing with regions of pure 3C-SiC. The simulation of the diffuse intensity allows to determine both the volume fraction of transformed material and the transformation level within these regions. It is further shown that the evolution with time and temperature of the transition implies the multiplication and glide of partial dislocations, the kinetics of which are quantified by means of DXS.
Raman Scattering and X-Ray Absorption from CVD Grown 3C-SiC on Si
Authors: Feng Zhe Chuan , Chen Cheng , Xu Qiang , Mendis Suwan P. , Jang Ling Yun , Tin Chin Che , Lee Kung Yen , Liu Chee Wee , Wu Zhengyun , Qiu Zhi Ren
Published: May 2012

FTIR, Visible and UV Raman scattering, as well as synchrotron radiation X-ray absorption, in combination, have been employed to investigate a series of CVD grown 3C-SiC/Si (100). Significant results on the optical and atomic bonding properties are obtained from these comparative studies.
4H-SiC Wafers Studied by X-Ray Absorption and Raman Scattering
Authors: Xu Qiang , Sun Hua Yang , Chen Cheng , Jang Ling Yun , Rusli E. , Mendis Suwan P. , Tin Chin Che , Qiu Zhi Ren , Wu Zhengyun , Liu Chee Wee , Feng Zhe Chuan
Published: May 2012

Synchrotron radiation X-ray absorption and UV 325 nm excitation Raman scattering- photoluminescence (PL) have been employed to investigate a series of 4H-SiC wafers, including bulk, epitaxial single or multiple layer structures by chemical vapor deposition. Significant results on the atomic bonding and PL-Raman properties are obtained from these comparative studies.
Mechanical Properties of Cubic SiC, GaN and AlN Thin Films
Authors: Pezoldt Joerg , Grieseler Rolf , Schupp Thorsten , As Donat J. , Schaaf Peter
Published: May 2012

Cubic polytypes of SiC, GaN and AlN were grown on silicon by molecular beam epitaxy. The mechanical properties of the epitaxial layers were investigated by nanoindentation. For 3C-SiC grown on Si(111) and Si(100) a dependence of the mechanical properties on the surface preparation with germanium prior to the carbonization was obtained.
Extended Characterization of the Stress Fields in the Heteroepitaxial Growth of 3C-SiC on Silicon for Sensors and Device Applications
Authors: Camarda Massimo , Anzalone Ruggero , Piluso Nicolò , Severino Andrea , Canino Andrea , La Via Francesco , La Magna Antonino
Published: May 2012

Using several characterization techniques (μ-Raman, mechanical profilometer and microstructure deflections) together with a recent stress model[ ] we study the heteroepitaxial growth of cubic silicon carbide on silicon (100). We show that the observed inconsistency between experimental results might be the result of defects generated on the silicon substrate during the carbonization process. In such a situation wafer curvature techniques do not allow the determination of the stress field in the grown films neither quantitatively nor qualitatively.
Micro-Raman Analysis of a Micromachined 3C-SiC Cantilever
Authors: Piluso Nicolò , Anzalone R. , Camarda Massimo , Severino A. , D'Arrigo Giuseppe , La Magna Antonino , La Via F.
Published: May 2012

In this work, Raman microscopy is used to study the stress distribution on 3C-SiC cantilevers. Also we compare the strain distribution observed on the microstructure, using the shift of the transverse optical (TO) mode in micro-Raman maps, with the values predicted using a recent analytic theory [1]. Along the width of the cantilever is observed a reduction of stress ascribed to the etching processes that removes a thin layer of the interface between the 3C-SiC film and the substrate close to the edge of the microstructure. It is possible to show that this variation can be ascribed to a non-linearity of the strain field along the 3C-SiC film thickness. Also, helped by Finite Element Modelling (FEM), we determined the stress tensor along the cantilever. This result shows that, for a complete stress description of the cantilevers, it is necessary taking into account the role of diagonal and off-diagonal stress tensorial components.
Single-Crystal SiC Resonators by Photoelectrochemical Etching
Authors: Islam Mohammad M. , Huang Chih Fang , Zhao Feng
Published: May 2012

In this paper, we report single-crystal 4H-SiC resonant structures fabricated by dopant-selective photoelectrochemical etching. The frequency response of the resonant beams was characterized by a dynamic scanning method using AFM with the beams excited by a piezoelectric actuator under atmosphere pressure and room temperature. The beam with a length of 35 μm shows mechanical resonance at 945 kHz. The Young’s modulus of single-crystal SiC was derived from the measured resonant frequency. Single-crystal 4H-SiC resonators developed in this study fully exploit the excellent electrical, mechanical, and chemical properties of SiC, while dopant-selective photoelectrochemical etching technique significantly simplifies the fabrication process.
Stable Growth of 4H-SiC Single Polytype by Controlling the Surface Morphology Using a Temperature Gradient in Solution Growth
Authors: Yamamoto Yuji , Seki Kazuaki , Kozawa Shigeta , Alexander Alexander , Harada Shunta , Ujihara Toru
Published: May 2012

We introduce a method to grow 4H-SiC single polytype stably by controlling the surface morphology. The polytype transition on on-axis 4H-SiC C-face was investigated from a viewpoint of surface morphology of grown layers. At the area where several hillock-like structures grew adjacently, the polytype transition from 4H-SiC to 6H-SiC or 15R-SiC often occurred. Therefore, we tried a modified seeded method to suppress the formation of hillock-like structures. As a result, the hillock-like structure on the grown layer was dramatically reduced. Moreover, the ratio of 4H-SiC polytype to the whole grown surface was increased to be almost 100%.
Radiation Hardness of Wide-Bandgap Materials as Exemplified by SiC Nuclear Radiation Detectors
Authors: Ivanov Alexander M. , Sadokhin Anton V. , Strokan Nikita B. , Lebedev Alexander A. , Kozlovski Vitalii V.
Published: May 2012

Polarization effect characteristically occurs in detectors based on wide-bandgap materials at considerable concentrations of radiation defects. The appearance of an electromotive force in the bulk of a detector is due to the long-term capture of carriers at deep levels related to radiation centers. The kinetics and strength of the polarization field have been determined. The capture can be controlled by varying the detector temperature, with a compromise reached at the "optimal" temperature between the generation current and the position of the deepest of the levels whose contribution to the loss of charge via capture is negligible. It has been found that the depth of a level (related to the energy gap width) is close to 1/3, irrespective of a material. The optimal temperatures are strictly individual for materials.
Emission Enhancement of SiC/SiO2 Core/Shell Nanowires Induced by the Oxide Shell
Authors: Fabbri Filippo , Rossi Francesca , Attolini Giovanni , Bosi Matteo , Salviati Giancarlo , Iannotta Salvatore , Aversa L. , Verucchi R. , Nardi M. , Fukata Naoki , Dierre Benjamin , Sekiguchi Takashi
Published: May 2012

In this work we report the enhancement of the 3C-SiC band edge luminescence induced by the SiO2 shell in SiC/SiO2 core/shell nanowires (NWs) system. We demonstrate that the shell enhances the SiC near band edge luminescence and we argue the formation of a type-I quantum well between the SiC core and the SiO2 shell, with the consequent injection of carriers from the larger band-gap shell to the narrower band-gap core.
Control of Void Formation in 4H-SiC Solution Growth
Authors: Mitani Takeshi , Okamura Masayuki , Takahashi Tetsuo , Komatsu Naoyoshi , Kato Tomohisa , Okumura Hajime
Published: May 2012

Void formation in 4H-SiC crystals grown from solution has been investigated by secondary ion mass spectrometry and Raman scattering. It becomes clear that ambient Ar gas is filled in voids and the solvent (Si) partially remains. The result indicates that Ar dissolved in the solvent vaporizes and forms bubbles. The trapped bubbles at the crystal growth front are considered to be incorporated in the growing crystal as voids. We also have developed following methods for suppression of the void formation; (1) dipping seed crystals so that the growth front faces upward, (2) growth under He atmosphere, and (3) the high temperature treatment of the solvent before crystal growth.
Morphological Instability of 4H-SiC (0001) Basal Plane Surface during Si-Vapor Thermal Etching
Authors: Ushio Shoji , Nakanishi Kohei , Ohtani Noboru , Kaneko Tadaaki
Published: May 2012

The morphological instability appeared at step-free 4H-SiC (0001) surfaces was investigated. The step-free surfaces were fabricated at the bottom of inverted-mesa structure by the method combining a laser digging and Si-vapor etching. By repeated Si-vapor etching treatments, randomly created crater and maze structures were cyclically appeared at the step-free surfaces. These structures were distinctly classifiable by their depths from the step-free surfaces. Crater structures have 0.2 - 0.3 nm depth and maze structures have 0.5 nm depth. The morphological evolutions indicate the process of destruction of the step-free (0001) basal plane and generation of steps from step-free surfaces in the Si-vapor etching process.
First-Principles Analysis of Dissociative Absorption of HF Molecule at SiC Surface Step Edge
Authors: Inagaki Kouji , Pho Bui Van , Yamauchi Kazuto , Morikawa Yoshitada
Published: May 2012

It has been reported that SiC surface can be etched off in a concentrated aqueous solution of hydrogen fluoride with making contacts with Pt plate catalyst, named Catalyst-referred Etching (CARE) [1]. In this report, we present first-principles molecular-dynamic simulations on the initial stage of the etching process. Reaction barrier heights of dissociative absorption reactions of hydrogen fluoride molecule breaking into back-bonds at step edge of 3C-SiC(111) are analyzed.
Characterization of Photoelectrochemical Properties of SiC as a Water Splitting Material
Authors: Yasuda Tomonari , Kato Masashi , Ichimura Masaya
Published: May 2012

Hydrogen energy attracts attention as an eco-friendly energy resource. The water splitting by semiconductor materials can generate hydrogen without CO2 emission. However, the hydrogen conversion efficiency using conventional materials is not high enough, or the materials corrode easily even if they show high efficiency. On the other hand, silicon carbide (SiC) is expected to be a water splitting material showing high conversion efficiency without corrosion. In this study, we characterized band edge potentials for 4H-, 6H- and 3C-SiC, and we revealed that they are capable of water splitting. We also estimated conversion efficiencies by photocurrent measurements in electrolytes for bulk 4H- and 6H-SiC.
Spatially Graded Graphitization on 4H-SiC (0001) with Si-Sublimation Gradient for High Quality Epitaxial Graphene Growth
Authors: Ushio Shoji , Kutsuma Yasunori , Yoshii Arata , Tamai Naoto , Ohtani Noboru , Kaneko Tadaaki
Published: May 2012

We report a new approach to produce high quality epitaxial graphene based on the concept of controlling Si sublimation rate from SiC surface. By putting a mask substrate to suppress Si sublimation from the SiC surface in ultrahigh vacuum, epitaxial graphene growth at 4H-SiC (0001) was locally controlled. Spatially graded surface graphitization was confirmed in a scanning electron microscopy contrast from the outside unmasked region to the inside masked region. The contrast was discussed with Raman characterization as the increase of graphene thickness and the surface compositional change of SiC. Results indicate two types of growth processes of epitaxial graphene at 4H-SiC (0001) step-terrace structures.
Top-Seeded Solution Growth of 4H-SiC Bulk Crystal Using Si-Cr Based Melt
Authors: Daikoku Hironori , Kado M. , Sakamoto H. , Suzuki Hiroshi , Bessho T. , Kusunoki K. , Yashiro N. , Okada N. , Moriguchi K. , Kamei K.
Published: May 2012

We have grown high-quality long cylindrical (12 mm thick) 4H-SiC bulk crystals by the meniscus formation technique, which was first applied for the solution growth of bulk SiC. It enabled long-term growth by suppressing parasitic reactions such as polycrystal precipitation around the seed crystal. In addition, we could control the growth angle from −22° to 61° by adjusting the meniscus height. The thickness of the grown cylindrical crystals was 12 mm, which is the largest reported until now, and corresponded to a growth rate of 0.6 mm/h. Smooth morphology growth was maintained on the (000-1) C-face. In cross-sectional transmission optical microscopy images, few solvent inclusions and voids were observed. XRD measurements revealed that the FWHM values of the grown crystals were almost the same as those of the seed crystal.
Structural and Electrical Properties of Graphene Films Grown by Propane/Hydrogen CVD on 6H-SiC(0001)
Authors: Michon Adrien , Roudon Elodie , Portail Marc , Jouault Benoit , Contreras Sylvie , Chenot Sébastien , Cordier Yvon , Lefebvre Denis , Vézian Stephane , Zielinski Marcin , Chassagne Thierry , Camassel Jean
Published: May 2012

We have grown graphene on SiC(0001) using propane-hydrogen CVD. In this work, we present the effects of growth pressure and temperature on structural and electrical properties. Structural characterizations evidence the formation of graphene with in-plane rotational disorder, except for low growth pressure and high growth temperature which lead to the formation of a (6Ö3´6Ö3)-30° interface between graphene and SiC. Electrical properties of samples presenting different graphene/SiC stacking and interfaces are compared and discussed.