bluuebunny/crossref_metadata_2025 huggingface dataset:
Bulk 3C-SiC Crystal by Top Seeded Solution Growth Method
Authors: Seki Kazuaki , Harada Shunta , Ujihara Toru
Published: March 2013

In this paper, we review our researches on the high-quality 3C-SiC bulk crystal growth. The polytype control and the suppression of defects are essential in the growth 3C-SiC on hexagonal SiC seed crystals. The growth polytype of SiC is usually controlled by the inheritance of the seed crystal. In contrast, we established kinetic polytype control in which the preferential growth of 3C-SiC can be achieved by the difference in the growth rates depending on supersaturation for the polytypes. In the growth of 3C-SiC, double positioning boundaries (DPBs) are often formed by the existence of twinned domain. The elimination of DPBs can be achieved utilizing the anisotropy of the step advance velocity.
Microsecond Carrier Lifetimes in Bulk-Like 3C-SiC Grown by Sublimation Epitaxy
Authors: Sun Jian Wu , Kamiyama Satoshi , Wellmann Peter J. , Liljedahl Rickard , Yakimova R. , Syväjärvi Mikael
Published: March 2013

High quality bulk-like 3C-SiC were grown on on-axis (0001) 6H-SiC substrate by sublimation epitaxy. The microwave photoconductivity decay mapping measurements revealed that this material shows considerable long carrier lifetimes varied from 3.519 to 7.834 μs under the injection level of 3.5×1012 cm-2, which are comparable with the best carrier lifetimes in 4H-SiC layers. The mapping of high resolution x-ray diffraction obtained from the same region shows that smaller carrier lifetimes seem to correspond to the larger FWHM values and vice versa. This shows that long carrier lifetime obtained in 3C-SiC is due to the improvement of the crystal quality.
Structural Investigation of Heteroepitaxial 3C-SiC Grown on 4H-SiC Substrates
Authors: Jacobson Henrik , Li Xun , Janzén Erik , Henry Anne
Published: March 2013

3C-SiC epilayers grown on Si-face nominally on-axis 4H-SiC substrate are characterized with X-ray diffraction techniques. The aim was to investigate if these 3C-SiC epilayers were grown by single domain growth. The results show that all samples start by having several nucleation centers all over the substrate surface and the growth continues with two domain formations. As the growth proceeds one domain overtakes the growth and single domain crystal growth occurs. This single domain was further investigated and the results show that it seems to contain many sub-domains with same lattice constant but slightly tilted.
High-Rate Rotated Epitaxy of 3C-SiC(111) on Si(110) Substrate for Qualified Epitaxial Graphene on Silicon
Authors: Suemitsu Maki , Sanbonsuge Shota , Saito Eiji , Jung Myung Ho , Fukidome Hirokazu , Filimonov Sergey
Published: March 2013

In the formation of epitaxial graphene on Si substrates, the growth of high-quality 3C-SiC thin films on Si substrates is a key to success. As a solution to the large mismatch between the Si substrate and the 3C-SiC film, rotated epitaxy in which 3C-SiC(111) films are grown on Si(110) substrates is quite attractive. In some applications, on the other hand, a certatin thickness (~100 nm or more) is required for this 3C-SiC films as well. A two-step growth method has been thus developed to realize a high-rate, qualified rotated epitaxy. A qualified graphene is found to be formed on this rotated epi-film, as typified by the increase of the grain size by a factor of 1.6 from the non-rotated epitaxy.
Rotated Epitaxy of 3C-SiC(111) on Si(110) Substrate Using Monomethylsilane-Based Gas-Source Molecular-Beam Epitaxy
Authors: Sambonsuge Shota , Saito Eiji , Jung Myung Ho , Fukidome Hirokazu , Filimonov Sergey , Suemitsu Maki
Published: March 2013

3C-SiC is the only polytype that grows heteroepitaxially on Si substrates and, therefore, it is of high interest for various potentail applications. However, the large (~20 %) lattice mismatch of SiC with the Si substrate causes a serious problem. In this respect, rotated epitaxy of 3C-SiC(111) on the Si(110) substrate is highly promising because it allows reduction of the lattice mismatch down to a few percent. We have systematically searched the growth conditions for the onset of this rotated epitaxy, and have found that the rotaed epitaxy occurrs at higher growth temperatures and at lower source-gas pressures. This result indicates that the rotated epitaxy occurs under growth conditions that are close to the equilibrium and is thefore thermodynamically, rather than kinetically, driven.
Raman Investigation of Aluminum-Doped 4H-SiC
Authors: Juillaguet Sandrine , Kwasnicki Pawel , Peyre Hervé , Konczewicz Leszek , Contreras Sylvie , Zielinski Marcin , Camassel Jean
Published: March 2013

Raman scattering spectra have been collected on p-type 4H-SiC samples doped with aluminum up to 5×1019 atoms per cubic cm. The distortion and asymmetry of FTA modes which appear in the low frequency range has been probed in great details. We show that, using standard Fano formulae with three parameters per mode, one can successively fit all FTA modes profiles in the concentration range 2×1016 – 5×1019 Al.cm-3.
An EPR Study of Defects in Neutron-Irradiated Cubic SiC Crystals
Authors: Bratus Victor , Melnyk Roman , Okulov Sergii , Shanina Bela , Golub Volodymyr , Makeeva Iryna
Published: March 2013

EPR spectroscopy has been used to characterize neutron-irradiated cubic SiC samples after thermal annealing in the 200-1100OC temperature range. Three new paramagnetic defects named Ky6, Ky7 and Ky8 have been revealed. Based on the present results, these defects have been tentatively attributed to the negatively charged carbon vacancy-carbon antisite pair, negatively charged divacancy and neutral carbon <100> split interstitial, respectively. Furthermore, the finding of practically isotropic hyperfine splitting for EPR lines of the T6 center confirms its assignment as a carbon vacancy-interstitial pair.
Optical Characterization of Compensating Defects in Cubic SiC
Authors: Ščajev Patrik , Jarašiūnas K. , Abramov P.L. , Lebedev S.P. , Lebedev Alexander A.
Published: March 2013

We present investigation of carrier recombination and optical trap recharge in sublimation grown n- and p-type 3C layers by using time-resolved nonlinear optical techniques. Carrier lifetime and recharged trap recovery were measured by differential transmittivity technique. By monitoring nonequilibrium carrier dynamics, we analyzed impact of carrier density and temperature on carrier lifetime and recharged trap recovery rate. Large carrier lifetime and small diffusivity at low injections in highly compensated samples and their dependences on injection were explained by optical recharge of compensating aluminum impurities. The complete recharge of the compensating impurities by optical means allowed us to calculate the compensating aluminum density in n-type samples and compensating nitrogen in p-type ones.
Origins of Negative Fixed Charge in Wet Oxidation for SiC
Authors: Kamiya Katsumasa , Ebihara Yasuhio , Chokawa Kenta , Kato Shigenori , Shiraishi Kenji
Published: March 2013

We demonstrate that the formation of carbonate-like moiety in SiO2 could be the origin of negative fixed charge in SiC thermal wet oxidation, based on first-principles calculations. We find that negative CO3 ion appears in SiO2 due to not only the existence of residual C atoms that are expected to be emitted from the SiC/SiO2 interface, but also a large enough number of incorporated H atoms during wet oxidation.
Subsurface Atomic Structure of 4H-SiC (0001) Finished by Plasma-Assisted Polishing
Authors: Deng Hui , Yamamura Kazuya
Published: March 2013

Plasma-assisted polishing (PAP) was proposed for finishing difficult-to-machine materials, such as single-crystal SiC, reaction-sintered SiC, diamond, and sapphire. In the case of PAP application to the finishing of the 4H-SiC surface, an atomically smooth surface without any scratches was obtained. In this study, we observed 4H-SiC (0001) surfaces processed by water vapor plasma oxidation and PAP using ceria abrasives through cross-sectional transmission electron microscopy (XTEM). Water vapor plasma oxidation was conducted for 1 min, 5 min and 60 min. An intermediate layer located between SiO2 and SiC, which corresponds to silicon oxycarbide, was clearly observed in the case of a short oxidation. As oxidation time increased from 1 min to 60 min, average oxidation rate decreased from 2.7 nm/min to 0.6 nm/min. An atomically smooth 4H-SiC (0001) surface was obtained after PAP for 60 min using ceria abrasives.
Superhyperfine Interactions of the Nitrogen Donors in 4H SiC Studied by Pulsed ENDOR and TRIPLE ENDOR Spectroscopy
Authors: Savchenko Dariya V. , Kalabukhova Ekaterina N. , Mokhov Evgeniy , Pöppl Andreas
Published: March 2013

The nitrogen donors residing at quasi-cubic lattice site (Nk) in 4H SiC were investigated by field sweep electron spin echo (FS ESE), pulsed electron nuclear double resonance (ENDOR) and pulsed General TRIPLE ENDOR spectroscopy. The 29Si and 13C superhyperfine lines observed in the FS ESE and ENDOR spectra of Nk in n-type 6H SiC were assigned by pulsed General TRIPLE resonance spectroscopy to the specific carbon (C) and silicon (Si) atoms located in the nearest environment of Nk in 4H SiC. The superhyperfine interaction constants and their relative signs for Nk with 29Si and 13C nuclei located in the nearest-neighbor shells are found from the General TRIPLE ENDOR spectra to be positive for C atoms and negative for Si atoms.
Temperature Dependence of Raman Scattering in 4H-SiC
Authors: Sun Hua Yang , Lien Siou Cheng , Qiu Zhi Ren , Feng Zhe Chuan
Published: March 2013

A series of 4H-SiC bulk wafers with different carrier concentrations were studied by Raman scattering in temperature range of 80K to 873K. Different Raman phonon modes of 4H-SiC can be clearly observed. Most Raman peaks of different modes shift to lower frequency with increasing temperature. But abnormal behavior can be observed in the longitudinal optical-plasma coupling mode, which does not decrease in frequency monotonously when temperature increases like other Raman modes. It increases at relatively low temperature and begins to drop after a critical temperature.
Theoretical Study of N Incorporation Effect during SiC Oxidation
Authors: Kato Shigenori , Chokawa Kenta , Kamaiya Katsumasa , Shiraishi Kenji
Published: March 2013

We investigated the atomistic mechanism of N incorporation during SiC oxidation by the first principles calculation. We found that N atoms play two characteristic roles in NO oxidation of SiC surface. One is that N atoms tend to form three-fold coordinated covalent bonds on a SiC(0001) surface, which assist the termination of surface dangling bonds, leading to improve the interface properties. The other is that N atoms form N-N bond like a double bond. The N2 molecule is desorbed from SiC surface, which do not disturb the oxidation process of SiC surfaces. These results indicate that N incorporation is effective to suppress defect state generation at SiO2/SiC interfaces during SiC oxidation.
To the Experimental Determination of the Spontaneous Polarization for the Silicon Carbide Polytypes
Authors: Davydov Sergey Yu. , Lebedev Alexander A. , Posrednik O.V.
Published: March 2013

A NH/3C-SiC heterojunction and a heterostructur of the NH/3C/NH type (N = 2, 4, 6, 8) are consid-ered. Two possibilities are analyzed for heterojunctions, in which a Si or a C is the contact plane of the NH polytype. In this case, the energies of the quasi-local levels in the quantum wells at the interface will be different. With the difference of these energies measured, it is possible to determine the spon-taneous polarization inherent in the NH polytype. In the presence of a spontaneous polarization field, the quasi-local levels in the left- and right-hand quantum wells of the heterostructure have dif-ferent energies. It is shown that, if the heterostructur is placed in an external electric field, it is possible to determine the magnitude of the spontaneous polarization by calculating the different between the energies of these levels. Experimental ways to find by using the suggested theoretical scenario are discussed.
A New-Type of Defect Generation at a 4H-SiC/SiO2 Interface by Oxidation Induced Compressive Strain
Authors: Chokawa Kenta , Kato Shigenori , Kamaiya Katsumasa , Shiraishi Kenji
Published: March 2013

Our message is oxidation process must be minimized as possible. Many carbon-related defect structures are reported in SiC/SiO2 interface. In this paper, we investigated the effect of oxidation to the defect forming by density functional theory (DFT). In the result, we found carbon defect structure that completely different from in the present report. This defect structure has carbon-carbon single bond with no dangling bond. To see the forming process, compressive strain from inserted oxygen atoms induce the rearrangement of structure and cause C-C defect structure. We can know that this structure is formed with energy gain about 3.8eV. And this C-C defect induces trap state under the conduction bottoms.
Effect of Interface Native Oxide Layer on the Properties of Annealed Ni/SiC Contacts
Authors: Huang Wei , Chang Shao Hui , Liu Xue Chao , Li Zheng Zheng , Zhou Tian Yu , Zheng Yan Qing , Yang Jian Hua , Shi Er Wei
Published: March 2013

The near-SiC-interfaces of annealed Ni/SiC contacts were observed directly by high-resolution transmission electron microscopy (HRTEM). 1 nm native oxide layer was observed in the as-deposited contact interface. The native oxide layer cannot be removed at 650°C through rapid thermal annealing (RTA) and it was completely removed at 1000°C RTA. The residue of native oxide layer resulted in the Schottky characters. High temperature annealing (>950°C) not only removes the oxide layer in the near-SiC-interface, but also forms a well arranged flat Ni2Si/SiC interface, which contribute to the formation of ohmic behavior.
Effect of Surface and Interface Recombination on Carrier Lifetime in 6H-SiC Layers
Authors: Sun Jian Wu , Kamiyama Satoshi , Yakimova Rositza , Syväjärvi Mikael
Published: March 2013

Carrier lifetimes in 6H-SiC epilayers were investigated by using numerical simulations and micro-wave photoconductivity decay measurements. The measured carrier lifetimes were significantly increasing with an increased thickness up to 200 μm while it stays almost constant in layers thicker than 200 μm. From a comparison of the simulation and experimental results, we found that if the bulk lifetime in 6H-SiC is around a few microseconds, both the surface recombination and interface recombination influence the carrier lifetime in layers with thickness less than 200 μm while only the surface recombination determines the carrier lifetime in layers with thickness more than 200 μm. In samples with varying thicknesses, a bulk lifetime = 2.93 μs and carrier diffusion coefficient D= 2.87 cm2/s were derived from the linear fitting of reciprocal lifetime vs reciprocal square thickness.
Electron Transport Features in Heterostructures 3C-SiC(n)/Si(p) at the Elevated Temperatures
Authors: Afanasyev A.V. , Ilyin Vladimir A. , Luchinin V.V. , Petrov A.S.
Published: March 2013

3C-SiC (n) / Si (p) heterostructures were obtained and investigated in a wide temperature range. It was shown, the main mechanisms of charge transport diffusion and recombination. The properties of silicon substrate were determining the working temperature range of investigated diodes. Therefore the rectifying properties of 3С-SiC(n)/Si(p) diodes were stable only up to 473 K. Two sites with different activation energies were observed on the Jrev(1/T) curves at fixed voltage: 0,32 eV which, characterized states on the SiC/Si interface, Е2 ≈ 0,55 eV which corresponds to the middle of silicon bandgap and defines existence of reverse current generation component.
Impact of AlN Spacer on Electron Mobility of AlGaN/AlN/GaN Structures on Silicon
Authors: Roensch Sebastian , Sizov Victor , Yagi Takuma , Murad Saad , Groh Lars , Lutgen Stephan , Krieger M. , Weber Heiko B.
Published: March 2013

The impact of the thickness of an AlN spacer in AlGaN/AlN/GaN high electron mobility transistor (HEMT) structures on the Hall mobility was investigated in a range of 30 K - 340 K. The AlN spacer has a strong impact on the mobility at temperatures below 150 K. This effect is linked to a reduction of alloy scattering. Optical and scanning electron microscopy revealed hexagonal shaped defects which also have an effect on the mobility. These defects can be avoided by an appropriate adjustment of the AlN layer thickness.
XPS Analysis of 4H-SiC Surfaces Oxidized by Helium-Based Atmospheric-Pressure Water Vapor Plasma for Plasma-Assisted Polishing
Authors: Deng Hui , Yamamura Kazuya
Published: March 2013

Plasma-assisted polishing (PAP) was successfully applied to single-crystal SiC to obtain an atomically flat surface without introducing any scratches. To clarify the flattening mechanism and increase the material removal rate (MRR) of PAP, investigation of the oxidation process in PAP is essential. In this study, we observed 4H-SiC (0001) surfaces processed by water vapor plasma oxidation using angle resolved X-ray photoelectron spectroscopy (ARXPS). Water vapor plasma oxidation was conducted for 1 min and 5 min. SiO2 and silicon oxycarbide were observed as the oxidation products. A decrease in the plasma irradiation time decreased the thickness of the oxide layer, particularly that of the silicon oxycarbide layer.
Interface Defects and Negative Bias Temperature Instabilities in 4H-SiC PMOSFETs – A Combined DCIV/SDR Study
Authors: Aichinger Thomas , Lenahan Patrick M. , Peters Dethard
Published: March 2013

We study the structure of SiC/SiO2 interface defects and the effects of negative bias temperature stress (NBTS) in lateral 4H silicon carbide (SiC) PMOSFETs. Our devices have 90 nm thick SiO2 gate oxides thermally grown in N2O ambient at 1280°C on n-type SiC. We investigate virgin (unstressed) and stressed devices using two different techniques: (i) for electrical characterization, we use the direct-current current-voltage (DCIV) technique [1] which measures a recombination current via interface defects and charge pumping (CP) which measures the number of interface defects within a certain range of the SiC band gap; (ii) to study the structure of the defects, we use electrically detected magnetic resonance (EDMR) via spin dependent recombination (SDR) [2]. The elevated temperature during NBTS is provided by in-situ heated test structures. This is the first EDMR study of p-doped SiC MOSFETs and the first negative bias temperature instability (NBTI) study of SiC MOSFETs using in-situ (on-chip) heating during stress.
Verification of Near-Interface Traps Models by Electrical Measurements on 4H-SiC n-Channel Mosfets
Authors: Uhnevionak Viktoryia , Strenger Christian , Burenkov Alex , Mortet Vincent , Bedel-Pereira Elena , Cristiano Fuccio , Bauer Anton J. , Pichler Peter
Published: March 2013

4H-SiC n-channel lateral MOSFETs were manufactured and characterized electrically by current-voltage measurements and by numerical simulation. To describe the observed electrical characteristics of the SiC MOSFETs, Near-Interface Traps (NIT) and mobility degradation models were included in the simulation. The main finding of the simulation is that two models for the NIT states in the upper part of the SiC bandgap are able to describe the electrical data equally well. In one of them, acceptor-like traps and fixed charge are considered while in a newly developed one, donor-like traps are taken into account also.
A Study of High Temperature DC and AC Gate Stressing on the Performance and Reliability of Power SiC MOSFETs
Authors: Green Ronald , Lelis A.J. , El M. , Habersat Daniel B.
Published: March 2013

Although high-temperature measurements show a dramatic reduction in the bias-temperature stress-induced threshold-voltage instability of present state-of-the-art devices, a more thorough test methodology shows that several different conclusions may actually be drawn. The particular conclusion depends on the specific post-BTS measurement technique employed. Immediate room-temperature measurements suggest that significant oxide-trap activation may still be occurring. A significant, yet rapid, post-BTS recovery is observed as well. These results underline the importance of making both high-temperature and room-temperature measurements, as a function of stress and recovery time, to better ensure that the full effect of the BTS is observed. Initial AC BTS results suggest a similar level of device degradation as occurs from a DC BTS.
Evidence of Tunneling in n-4H-SiC/SiO2 Capacitors at Low Temperatures
Authors: Filip Lucian Dragos , Pintilie Ioana , Svensson Bengt Gunnar
Published: March 2013

In this work, anomalous discontinuities observed in Capacitance-Voltage (C-V) characteristics on non-nitridated n-4H-SiC/SiO2 capacitors at low temperature are addressed. The appearance of abrupt capacitance minima, always at the same gate voltages (4V and 8V) and independent on probe frequency, led us to consider a resonant electron tunneling process from neutral donor states present at the SiC/SiO2 interface into two well defined energy levels in the oxide layer. Results of numerical simulations based on this model describe quantitatively the experimentally observed discontinuities at 4V and 8V and provide strong evidence for the presence resonant tunneling.
The Study of the Geometry and Growth Trend of Silicon Carbide Crystals
Authors: Fong Feng Jui , Chen Wun Yan , Tsao Shen , Hsiao Ta Ching , Huang Chih Fang
Published: March 2013

The study compared the influences of silicon materials from different sources on the crystal growth process and geometry of silicon carbide (SiC). As revealed by the results of the study, although the purity of commercial silicon material was as high as 11N, the rate of crystal growth was slow. However, if the silicon material made by electron beam refining metallurgical silicon was utilized for the SiC crystal growth experiment, the morphology of SiC crystal was better and the rate of crystal growth was faster despite its purity being only about 4.5N.
Boron Diffusion in Silicon Carbide
Authors: Aleksandrov O.V. , Mokhov E.N.
Published: March 2013

For the description of features of boron diffusion of in silicon carbide the new two-component model is offer. The first component is the “shallow” boron - boron atoms in silicon sites (BSi). This component is prevailed in the surface region of diffusion layers and has rather low speed of diffusion. The second component is the “deep” boron – impurity-defect pairs of boron with carbon vacancy (BSi-VC). This component is prevailed in the volume region of diffusion layers and has rather high speed of diffusion. By means of model the influence of nitrogen impurity and isoconcentration diffusion of an isotope 10B are described.
Temperature Dependence of the Band-Edge Injection Electroluminescence of 4H-SiC pn Structure
Authors: Strel'chuk Anatoly M. , Kalinina Evgenia V. , Lebedev Alexander A.
Published: March 2013

We present the injection electroluminescence spectra in the temperature range 290-800 K of 4H-SiC pn structure, which was formed by implantation of Al+ ions in low-doped n-type conductivity 4H-SiC epitaxial layer. The dominant emission band of injection electroluminescence (IEL) spectrum at room temperature was observed in the blue-green region; as the temperature is raised, the blue-green band is quenched, while UV band (near band-edge) IEL become dominant. The peak parameters of UV band at room temperature are: hmax  3.17 eV, full width at half maximum w  90 meV. The UV peak shifted in the long-wave direction with increasing temperature; the hmax (T) dependence was linear with the slope of -2.3∙10-4 eV/K. Both the IEL intensity of the UV peak at hmax and band width w increased upon heating. The w(T) dependence was linear with the slope of 2.9∙10-4 eV/K; intensity increased with the activation energy of 100-150 meV. The UV IEL band can be considered more probable to the band-band recombination and edge IEL increasing with rising temperature can be explained by the nonequilibrium charge carriers lifetime increasing.
A Possible Mechanism for Hexagonal Void Movement Observed during Sublimation Growth of SiC Single Crystals
Authors: Fujimoto Tatsuo , Tsuge Hiroshi , Katsuno Masakazu , Sato Shinya , Yashiro Hirokatsu , Hirano Hosei , Yano Takayuki
Published: March 2013

A possible mechanism of hexagonal void movement during Physical vapor transport (PVT)-growth is proposed in terms of quasi-equilibrium phase transition process based upon the Si-C binary phase diagram. The hexagonal void movement can be realized when two different reactions occurs simultaneously: (1) SiC(s) solidification and (2) decomposition without graphitization. Further, the kinetic instability of the void movement observed is also discussed, and found to be explainable if the effect of the temperature gradient existing in the crystal grown in conventional PVT-process is included.
Aluminum Implantation in 4H-SiC: Physical and Electrical Properties
Authors: Michaud Jean François , Song X. , Biscarrat J. , Cayrel F. , Collard Emmanuel , Alquier D.
Published: March 2013

For this study, 4H SiC samples were implanted with aluminum at room temperature, 200°C and 600°C with different energies, ranging from 30 to 380 keV, for a total dose of 4x1015 cm 2, to create a “box-like” profile. To activate dopants, samples were then isochronally annealed from 1650°C to 1850°C during 30min. The lowest specific contact resistance achieved, evaluated to 1.3x10-5 Ω.cm2, has been obtained for the 200°C implanted sample annealed at 1850°C. For this condition, Scanning Capacitance Microscopy study has proved that the dopant activity is quite homogeneous in opposition with the samples implanted at RT and 600°C.
Characterization of (4,4)- and (5,3)-Type Stacking-Faults in 4deg.-Off 4H-SiC Epitaxial Wafers by Synchrotron X-Ray Topography and by Photo-Luminescence Spectroscopy
Authors: Yamashita T. , Matsuhata H. , Miyasaka Y. , Odawara M. , Momose K. , Sato T. , Kitabatake M.
Published: March 2013

Experimentally,the grazing-incident X-ray topography at different diffraction conditions, and room temperature photo-luminescence spectroscopy, various different types of stacking-faults in epitaxial films on 4-degrees-off 4H-SiC wafers were identified precisely without wafer cutting. Their types and the numbers were investigated statistically. It became clear that (4,4) type stacking-faults were the most common ones and two different types were identified. Still 34% of the stacking-faults were unknown types in the present investigation.Several different kinds of stacking-faults formed on the surface of 4-degrees-off 4H-SiC epitaxial wafers were investigated. Their types could be identified and type distribution in a wafer could be obtained using X-ray topography and room temperature Photo-Luminescence without wafer cutting. Type determination of 8H(4,4)- stacking fault ; with or without strain field, could also be decideddemonstrated using this method.
Dielectric Properties of Thermally Grown SiO2 on 4H-SiC(0001) Substrates
Authors: Hosoi Takuji , Uenishi Yusuke , Mitani Shuhei , Nakano Yuki , Nakamura Takashi , Shimura Takayoshi , Watanabe Heiji
Published: March 2013

The bulk properties of thermally grown SiO2 on 4H-SiC(0001) substrates were thoroughly investigated by capacitance-voltage (C-V) measurement, atomic force microscopy (AFM), spectroscopic ellipsometry (SE), x-ray photoelectron spectroscopy (XPS), and secondary ion mass spectrometry (SIMS). The equivalent oxide thickness (EOT) extracted from the capacitance-voltage (C-V) characteristics of TiN/SiO2 capacitors was proportional to the physical thickness (Tphys), but the slope of the linear fit was found to be 1.11, indicating that the permittivity of SiO2 on 4H-SiC formed by thermal oxidation is only about 3.5, which is lower than the commonly accepted value of 3.9. Since XPS analysis revealed that the oxide of SiC was stoichiometric and the atomic concentration of residual carbons in the oxide measured by SIMS was sufficiently low (1017 cm-3), the low permittivity of thermal oxides of 4H-SiC may originate from the reduced bulk density, which can be predicted by the Clausius-Mossotti relation.
Effects of Al Ion Implantation on 3C-SiC Crystal Structure
Authors: Severino Andrea , Piluso Nicolò , Marino Antonio , La Via Francesco
Published: March 2013

In this study, a 6 inch 3C-SiC wafer has been grown and processed to realize an Al+-implanted layer underneath the film surface. The structural damaging has been carefully analyzed by X-Ray Diffraction (XRD) and micro-Raman spectroscopy. Raman analysis on a grazing angle polished film, after the implantation process, has been conducted and a spectral region (between 825 and 925 cm-1) has been identified as an interesting footprint of the crystal damaging. Thermal treatments on implanted samples at doses as low as 4x1014 cm-2 have shown a capability of the 3C-SiC crystal structure to recover from damaging. Reciprocal space mapping on (004) 3C-SiC lattice points suggests a total recovery at an annealing temperature of 1350 °C.
Electrical Characterisation of Epitaxially Grown 3C-SiC Films
Authors: Jiang Liu Di , Zhong Le , Reed Fred , Taysir Salim , Bosi Matteo , Attolini Giovanni
Published: March 2013

3C-SiC have been epitaxially grown through vapour phase expitaxy under a different grow conditions. Key electrical properties of these SiC layers have been characterised by fabrication and measurement of metal-SiC-metal devices. The electrical properties of SiC grown at different conditions have been analysed based on their structural and crystalline quality.
Influence of Growth Temperature on Carrier Lifetime in 4H-SiC Epilayers
Authors: Lilja Louise , Hassan Jawad , Booker Ian D. , Bergman Peder , Janzén Erik
Published: March 2013

Carrier lifetime and formation of defects have been investigated as a function of growth temperature in n-type 4H-SiC epitaxial layers, grown by horizontal hot-wall CVD. Emphasis has been put on having fixed conditions except for the growth temperature, hence growth rate, doping and epilayer thickness were constant in all epilayers independent of growth temperature. An increasing growth temperature gave higher Z1/2 concentrations along with decreasing carrier lifetime. A correlation between growth temperature and D1 defect was also observed.
Introducing Color Centers to Silicon Carbide Nanocrystals for In Vivo Biomarker Applications: A First Principles Study
Authors: Somogyi Bálint , Zólyomi Viktor , Gali Adam
Published: March 2013

Molecule-sized fluorescent emitters are much sought-after to probe biomolecules in living cells. We demonstrate here by time-dependent density functional calculations that the experimentally achievable 1-2 nm sized silicon carbide nanocrystals can emit light in the nearinfrared region after introducing appropriate color centers in them. These near-infrared luminescent silicon carbide nanocrystals may act as ideal fluorophores for in vivo bioimaging.
Growth of Large Diameter 4H-SiC by TSSG Technique
Authors: Kusunoki Kazuhiko , Yashiro N. , Okada Nobuhiro , Moriguchi Kouji , Kamei Kazuhito , Kado Motohisa , Daikoku Hironori , Sakamoto Hidemitsu , Suzuki Hiroshi , Bessho Takeshi
Published: March 2013

4H-SiC single crystal with 3-inch diameter was grown by top seeded solution growth (TSSG) technique. We used a new convection control member called “Immersion Guide (IG)” which causes the high and homogenous fluid flow in the solution. As a result, we achieved relatively high growth rate and morphological stability
Photoluminescence Imaging and Discrimination of Threading Dislocations in 4H-SiC Epilayers
Authors: Nagano M. , Kamata Isaho , Tsuchida H.
Published: March 2013

Photoluminescence images and spectra of threading screw dislocations (TSDs) and threading edge dislocations (TEDs) were obtained and compared with synchrotron X-ray topography images. Discrimination between TSDs and TEDs by analysis of PL spot size in the imaging technique as well as PL spectra of the dislocations in a near infrared region is demonstrated. We also have succeeded in cross-sectional PL imaging of threading dislocations in a thick epilayer.
Piezoresistivity and Electrical Conductivity of SiC Thin Films Deposited by High Temperature PECVD
Authors: Jakovlev Oleg , Fuchs Tino , Rohlfing Franziska , Seidel Helmut
Published: March 2013

We introduce a novel high temperature PECVD process and use it for the deposition of silicon carbide thin films on oxidized silicon wafers at 900°C substrate temperature. A variation of the atomic composition over a wide range is achieved by altering the flow ratio of the precursors silane (SiH4) and acetylene (C2H2). XPS analysis is performed to verify the silicon to carbon ratio in the deposited layers. The resistivity of the obtained thin films shows a strong dependence on the Si/C-ratio. Four point measurements show the resistivity ranging between 5•10-3Ωcm for C-rich layers and >107Ωcm for near stoichiometric layers. We investigate the piezoresistivity of the SiC layers at room temperature under compressive and tensile strain using the four point bending method. The same method is used to analyze selected layers at elevated temperatures up to 600°C. Based on the results we evaluate the applicability of the obtained thin films for strain transducing in harsh environment MEMS sensors.
Radiation Defects Produced in 4H-SiC Epilayers by Proton and Alpha-Particle Irradiation
Authors: Hazdra Pavel , Záhlava Vít , Vobecký Jan , Berthou Maxime , Mihaila Andrei
Published: March 2013

Electronic properties of radiation damage produced in 4H-SiC epilayer by proton and alpha particle irradiation were investigated and compared. 4H-SiC epilayers, which formed the low doped n-base of Schottky barrier power diodes, were irradiated to identical depth with 550 keV protons and 1.9 MeV alphas. Radiation defects were then characterized by capacitance deep-level transient spectroscopy and C-V measurements. Results show that both projectiles produce identical, strongly localized damage peaking at ion’s projected range. Radiation defects have a negligible effect on dynamic characteristic of irradiated 4H-SiC Schottky diodes, however acceptor character of introduced deep levels and their high introduction rates deteriorate diode’s ON-state resistance already at very low irradiation fluences.
Reliability Investigation of Drain Contact Metallizations for SiC-MOSFETs
Authors: Sünner Thomas , Behrens Tim , Kaden Thomas
Published: March 2013

The reliability of silicon carbide vertical DMOS drain metallizations was investigated using conditions close to a possible application setup. We monitored the adhesion of silicon carbide dies with different contacts and metallizations that were silver-sintered to a copper substrate. The temperature range in an anticipated automobile application ranges between -40°C and 250°C and the reliability tests were performed for temperature dwelling at 250°C in air and temperature swings between -40°C and 200°C.
Stress Relaxation Study in 3C-SiC Microstructures by Micro-Raman Analysis and Finite Element Modeling
Authors: Piluso Nicolò , Anzalone Ruggero , Severino Andrea , Canino Andrea , La Magna Antonino , D'Arrigo Giuseppe , La Via Francesco
Published: March 2013

In this paper, micro-Raman characterizations and Finite element modeling (FEM) of microstructures (cantilever, bridge, planar rotating probe) realized on single-crystal (100) 3C-SiC/Si films are performed. Transverse optical (TO) Raman mode analysis reveals the stress relaxation on the free standing structure (796.5 cm-1) respect to the stressed unreleased region (795.7 cm-1). The TO Raman mode exhibits an intense shift, up to 2 cm-1, located on the undercut region, where the Silicon substrate starts to be released. Such effect is ascribed to the modification of the Raman stress tensor that makes the generalized axial regime, described by diagonal components of the Raman stress tensor, unsuitable to describe the stress status on this region. Raman maps analysis and FEM simulations show the “activation” of the shear stress, i.e. non-diagonal components of the stress tensor. The aim of future works will be to minimize the stress field generation and the defects density within the epitaxial layer.
SiC Sublimation Growth at Small Spacing between Source and Seed
Authors: Mokhov E.N. , Roenkov A.D. , Segal A.S.
Published: March 2013

The growth kinetics of SiC crystals doped with Al and Ga impurities and grown by the sublimation sandwich method at a small spacing between the source and the seed (<1 mm) has been studied. Dependence of an Al-doped SiC crystals growth rate on the clearance is shown to be non-monotonic and exhibits maximum at the clearance about of 100-300 μm. Such dependence is also observed for growth of pure and Ga-doped SiC crystals but only on (0001)Si face. The derived dependencies suggest that there are some considerable kinetic limitations of the SiC growth rate. High quality SiC crystals with such high concentration of the Al impurity as 2x1021 cm-3 were grown.
Influence of Post-Implantation Annealing Temperature on MOSFET Performance and Oxide Reliability
Authors: Grieb Michael , Noll Stefan , Scholten Dick , Rambach Martin
Published: March 2013

In the present work, we studied the influence of the post-implantation annealing temperature on the performance and oxide reliability of lateral 4H-SiC MOSFETs. The maximum field effect mobility of the MOSFETs at 25°C decreases from 22.4cm2/Vs to 17.2cm2/Vs by increasing annealing temperature from 1600°C to 1800°C. Respectively, the measured meantime to failure is about one order of magnitude higher for the 1700°C annealed sample at an applied field of 8.5MV/cm compared to the 1600°C and 1800°C annealed samples.
Investigation of Nitrided Atomic-Layer-Deposited Oxides in 4H-SiC Capacitors and MOSFETs
Authors: Haney Sarah Kay , Misra Veena , Lichtenwalner Daniel J. , Agarwal Anant K.
Published: March 2013

MOSFETs and capacitors have been fabricated to investigate the atomic layer depositon (ALD) of SiO2 onto SiC compared to thermal oxidation of SiC. Devices were fabricated on 4H-SiC with the following oxidation treatments: thermal oxidation at 1175°C, thermal oxidation at 1175°C followed by a nitric oxide (NO) anneal at 1175°C, and ALD of SiC at 150°C followed by an NO post oxidation anneal (POA) at 1175°C. ALD of the SiO2 was performed using 3-aminopropyltriethoxysiliane (3-APTES), ozone and water. Capacitors fabricated with NO annealed ALD oxide and thermal oxide with NO POA exhibited similar CV behavior and yielded similar Dit of 1e11 at 0.5 eV from the conduction band. MOSFETs fabricated with NO PDA ALD oxide exhibited peak field effect mobilities ranging from 32 – 40.5 cm2/Vs compared to 30 –34.5 cm2/Vs for the MOSFETs with NO annealed thermal oxide. The higher mobilities exhibited by the ALD gate oxides were linked through SIMS to higher nitrogen concentrations at the SiO2/SiC interface.
Effects of a Post-Oxidation Annealing in Nitrous Oxide on the Morphological and Electrical Properties of SiO2/4H-SiC Interfaces
Authors: Swanson Lukas K. , Fiorenza Patrick , Giannazzo Filippo , Alessandrino S. , Lorenti S. , Roccaforte Fabrizio
Published: March 2013

This work reports on the morphological, structural and electrical effects of a nitrous oxide (N2O) ambient post-oxidation annealing (POA) of the SiO2/4H-SiC interface. In particular, a conventional electrical characterization of MOS capacitors showed that nitrous oxide POA reduces the presence of both fixed oxide charge and the density of interface states. A local atomically flat interface was observed by transmission electron microscopy with only a moderate step bunching observed at a macroscopic scale. A novel nanoscale characterization approach via scanning spreading resistance microscopy resolved local electrical changes induced at the SiC surface exposed to N2O POA. This result subsequently revealed additional insight into the mechanism for the improved device performance subjected to N2O POA treatment.
Effect of NH3 Post-Oxidation Annealing on Flatness of SiO2/SiC Interface
Authors: Soejima Narumasa , Kimura Taishi , Ishikawa Tsuyoshi , Sugiyama Takahide
Published: March 2013

We investigated the effects of the post-oxidation annealing (POA) atmosphere on the electrical properties and interfacial roughness of SiO2 deposited on a 4H-SiC (0001) face and SiC. POA in ammonia (NH3) gave MOS capacitors with a lower interface trap density and n-channel MOSFETs with higher field-effect mobility than POA in nitrous oxide (N2O) or nitrogen (N2). In contrast, POA in N2O gave a lower interface trap density than POA in N2, but it gave the lowest field-effect mobility of all the samples. Cross-sectional TEM observations revealed that N2O POA gave a higher interfacial roughness than NH3 POA. We thus considered that N2O POA degraded the inversion-layer mobility due to increased roughness scattering.
Influence of Nitrogen Implantation on Electrical Properties of Al/SiO2/4H-SiC MOS Structure
Authors: Król Krystian , Sochacki Mariusz , Turek Marcin , Żuk Jerzy , Przewlocki Henryk M. , Gutt Tomasz , Borowicz Pawel , Guziewicz M. , Szuber Jacek , Kwoka Monika , Kościelniak Piotr , Szmidt Jan
Published: March 2013

In this article, an influence of nitrogen implantation dosage on SiC MOS structure is analyzed using wide range of nitrogen implantation dose (between ~1013 – 1016). Authors analyzed electrical and material properties of investigated samples using C-V, I-V measurements, Raman spectroscopy, and XPS profiling. It has been shown that surface state trap density is directly connected to implantation damage and thus implantation conditions. Using research results a trap origin at given energy can be concluded.
Effect of Suppressing Reoxidation at SiO2/SiC Interface during Post-Oxidation Annealing in N2O with Al2O3 Capping Layer
Authors: Kimura Taishi , Ishikawa Tsuyoshi , Soejima Narumasa , Nomura Katsuya , Sugiyama Takahide
Published: March 2013

In the present study, applying Al2O3 capping layer as suppressing layer of oxygen diffusion to SiC-MOS structures, we investigated the effect of Al2O3 layer as suppression of reoxidation at SiO2/SiC interface and decrease of Dit. We evaluated MOS capacitors which have SiO2/SiC and Al2O3/SiO2/SiC structure on 4H-SiC (0001) Si-face epitaxial wafers after post-oxidation anneal process (N2O:N2=1:9 [slm]) at temperatures ranging from 1000 °C to 1300 °C for 30min. The Al2O3/SiO2/SiC structure of reoxidation thickness, surface roughness and Dit are smaller than those of SiO2/SiC structure. These results show that the suppression of reoxidation during POA is important to improve the SiO2/SiC interfacial qualities.
Transition Metal Oxide-Diamond Interfaces for Electron Emission Applications
Authors: Tiwari Amit K. , Goss Jonathan P. , Briddon Patrick R. , Wright Nicholas G. , Horsfall Alton B. , Rayson Mark J.
Published: March 2013

Diamond surfaces with suitable adsorbed chemical species can exhibit both negative and positive electron affinities, arising from the complex electrostatic interplay between adsorbates and surface carbon atoms of diamond lattice. We presents the results of density functional calculations into the energetics and the electron affinity of diamond (100) surfaces terminated with the oxides of selected transition metals. We find that for a correct stoichiometry, oxides of transition metals, such as Ti and Zn, exhibit a large negative electron affinity of around 3 eV. The desorption of transition metal oxides is found to be highly endothermic. We therefore propose that transition metal oxides are promising for the surface coating of diamond-based electron emitters, as these exhibit higher thermal stability in comparison to the commonly used CsO terminations, while retaining the advantage of inducing a large negative electron affinity.
Al+ Implanted 4H-SiC: Improved Electrical Activation and Ohmic Contacts
Authors: Nipoti Roberta , Hallén Anders , Parisini Antonella , Moscatelli Francesco , Vantaggio Salvatore
Published: March 2013

The p-type doping of high purity semi-insulating 4H-SiC by Al+ ion implantation and a conventional thermal annealing of 1950 °C/5 min has been studied for implanted Al concentration in the range of 1 x1019 - 8 x 1020 cm-3 (0.36 μm implanted thickness). Sheet resistance in the range of 1.6 x 104 to 8.9 x102 Ω, corresponding to a resistivity in the range of 4.7 x 10-1 to 2.7 x 10-2 Ωcm for increasing implanted Al concentration have been obtained. Hall carrier density and mobility data in the temperature range of 140–600 K feature the transition from a valence band to an intra-band conduction for increasing implanted Al concentration. The specific contact resistance of Ti/Al contacts on the 5 x1019 cm-3 Al implanted specimen features a thermionic field effect conduction with a specific contact resistance in the 10-6 Ωcm2 decade.
Potentialities of Nickel Oxide as Dielectric for GaN and SiC Devices
Authors: Lo Nigro Raffaella , Greco Giuseppe , Swanson L. , Fisichella G. , Fiorenza Patrick , Giannazzo Filippo , Di Franco S. , Bongiorno C. , Marino A. , Malandrino G. , Roccaforte Fabrizio
Published: March 2013

This paper reports on a structural and electrical analysis of nickel oxide (NiO) films grown both on AlGaN/GaN heterostructures and on 4H-SiC epilayers. The films were grown by metal organic chemical vapor deposition (MOCVD). The structural analysis showed epitaxially oriented films over the hexagonal substrates. The electrical characterization of simple devices onto AlGaN/GaN heterostructures enabled to demonstrate a dielectric constant of 11.7 and a reduction of the leakage current in insulated gate structures. On the other hand, epitaxial NiO films grown onto 4H-SiC epilayers exhibited the presence of an interfacial SiO2 layer and twinned NiO grains, and a lower dielectric constant.
Filling of Deep Trench by Epitaxial SiC Growth
Authors: Kojima K. , Nagata A. , Ito S. , Sakuma Y. , Kosugi R. , Tanaka Yasunori
Published: March 2013

We performed deep trench filling by using epitaxial SiC growth. It was found that the trench filling condition depend on trench width. A high growth temperature was needed to fill a narrow trench and a low growth temperature was needed to fill a wide trench structure. We optimized the filling condition and successfully filled 7μ m deep and 2 μm wide trench without void formation. We also investigated the 2D doping distribution of the filled area by SSRM. As a result, it is found that the existence of a sub-trench was related to the generation of a doping distribution in the filled area. The trench filling mechanism and doping distribution are discussed.
Process Variation Tolerant 4H-SiC Power Devices Utilizing Trench Structures
Authors: Elahipanah Hossein , Salemi Arash , Buono Benedetto , Zetterling Carl Mikael , Östling Mikael
Published: March 2013

Silicon carbide (SiC) is one of the most attractive semiconductors for high voltage applications. The breakdown voltage of SiC-based devices highly depends on the variation of the fabrication process including doping of the epilayers and the etching steps. In this paper, we show a way to diminish this variability by employing novel trench structures. The influence of the process variations in terms of doping concentration and etching has been studied and compared with conventional devices. The breakdown voltage variation (ΔVBR) of 450 V and 2100 V is obtained for the ±20% variation of doping concentration of the devices with and without the trench structures, respectively. For ±20% variation in etching steps, the maximum ΔVBR of 380 V is obtained for the device with trench structures in comparison to 1800 V for the conventional structure without trench structures. These results show that the breakdown voltage variation is significantly reduced by utilizing the proposed structure.