bluuebunny/crossref_metadata_2025 huggingface dataset:
Sublimation Growth and Structural Characterization of 3C-SiC on Hexagonal and Cubic SiC Seeds
Authors: Vasiliauskas Remigijus , Marinova Maya , Syväjärvi Mikael , Mantzari Alkyoni , Andreadou Ariadne , Lorenzzi Jean , Ferro Gabriel , Polychroniadis Efstathios K. , Yakimova Rositza
Published: May 2010

Epitaxial growth of cubic silicon carbide on 6H-SiC substrates, and 6H-SiC substrates with (111) 3C-SiC buffer layer, deposited by vapour liquid solid mechanism, was compared. The morphological details of the grown layers were studied by optical microscopy and their microstructure by transmission electron microscopy. The influence of the substrate on the nucleation of 3C-SiC, the initial homoepitaxial 6H-SiC nucleation before 3C-SiC as well as the formation of defects, are discussed.
Identification of Defects Limiting the Carrier Lifetime in n- Epitaxial Layers of 4H-SiC
Authors: Klein Paul B.
Published: May 2010

The identification of defects limiting the carrier lifetime in n- epilayers of 4H-SiC is reviewed. The dominant electron traps, the Z1/2 and EH6/7 defects, believed to be VC-related, have been correlated to the lifetime in several studies. It was later shown that only one center, Z1/2 , actually controls the bulk lifetime. In recently-grown material with low Z1/2 concentration, other processes dominate. Recent measurements indicate that surface recombination controls the lifetime.
Temperature Dependence of the Carrier Lifetime in 4H-SiC Epilayers
Authors: Klein Paul B. , Myers-Ward Rachael L. , Lew Kok Keong , VanMil Brenda L. , Eddy Charles R. , Gaskill D. Kurt , Shrivastava Amitesh , Sudarshan Tangali S.
Published: May 2010

The temperature dependence of the carrier lifetime was measured in n-type 4H-SiC epilayers of varying Z1/2 deep defect concentrations and layer thicknesses in order to investigate the recombination processes controlling the carrier lifetime in low- Z1/2 material. The results indicate that in more recently grown layers with lower deep defect concentrations, surface recombination tends to dominate over carrier capture by other bulk defects. Low-injection lifetime measurements were also found to provide a convenient method to assess the surface band bending and surface trap density in samples with a significant surface recombination rate.
Electronic Properties of Femtosecond Laser Induced Modified Spots on Single Crystal Silicon Carbide
Authors: Tomita Takuro , Iwami M. , Yamamoto M. , Deki M. , Matsuo Shigeki , Hashimoto Shuichi , Nakagawa Y. , Kitada T. , Isu T. , Saito S. , Sakai K. , Onoda Shinobu , Ohshima Takeshi
Published: May 2010

Femtosecond (fs) laser modification on single crystal silicon carbide (SiC) was studied from the viewpoints of electric conductivity. Fourier transform infrared (FTIR) spectroscopy was carried out on femtosecond laser modified area. The intensity decrease of reststrahlen band due to the modification was observed, and this decrease was explained by the degradation of crystallinity due to the laser irradiation. Polarization dependence of reststrahlen band was also observed on laser modified samples. Current-voltage characteristics and Hall measurements on fs-laser modified region were carried out by fabricating the metal contacts on the ion implanted areas. The specific resistance up to 5.9×10-2 m was obtained for fs-laser modified area.
Calculation of Lattice Constant of 4H-SiC as a Function of Impurity Concentration
Authors: Matsumoto Tsubasa , Nishizawa Shin Ichi , Yamasaki Satoshi
Published: May 2010

Calculations of lattice constant of 4H-SiC and diamond have been carried out. Lattice constant of 4H-SiC trends to decrease when nitrogen concentration increases. On the other hand, lattice constant of 4H-SiC trends to increase when aluminum concentration increases. Lattice constant of boron and phosphorus doped diamond trends to increase when impurity concentration increases. The effect of phosphorus on diamond lattice constant is about six times larger than that of boron.
Low Temperature near Band Gap Photoluminescence of 3C-SiC/15R-SiC and 3C-SiC/6H-SiC Heterostructures
Authors: Lebedev Alexander A. , Abramov Pavel L. , Bogdanova Elena V. , Davydov Sergey Y. , Lebedev Sergey P. , Nelson Dmitrii K. , Oganesyan Gagik A. , Razbirin Boris S. , Tregubova Alla S.
Published: May 2010

Photoluminescence (PL) spectra of 3C-SiC(n,p)/6H-SiC(n) and 3C-SiC(p)/15R-SiC(n) heterostructures have been studied. A broad structureless band, absent in PL spectra of n–n heterostructures, was observed in the spectrum of p–n heterostructures in the energy range 2.2–2.4 eV. It is suggested that this band is due to the presence of a 2D electron gas in a quantum well near the heterointerface. High (~ 4000 cm2/s V) value of electron mobility and the absence of any significant fall in the mobility temperature dependence at liquid-nitrogen temperatures confirm the existence of a 2DEG in the QW at the heterointerface.
A Pictorial Tracking of Basal Plane Dislocations in SiC Epitaxy
Authors: Stahlbush Robert E. , Myers-Ward Rachael L. , VanMil Brenda L. , Gaskill D. Kurt , Eddy Charles R.
Published: May 2010

The recently developed technique of UVPL imaging has been used to track the path of basal plane dislocations (BPDs) in SiC epitaxial layers. The glide of BPDs during epitaxial growth has been observed and the role of this glide in forming half-loop arrays has been examined. The ability to track the path of BPDs through the epitaxy has made it possible to develop a BPD reduction process for epitaxy grown on 8° offcut wafers, which uses an in situ growth interrupt and has achieved a BPD reduction of > 98%. The images also provide insight into the strong BPD reduction that typically occurs in epitaxy grown on 4° offcut wafers.
Systematic First Principles Calculations of the Effects of Stacking Fault Defects on the 4H-SiC Band Structure
Authors: Camarda Massimo , Delugas Pietro , Canino Andrea , Severino Andrea , Piluso Nicolò , La Magna Antonino , La Via Francesco
Published: May 2010

Shockley-type Stacking faults (SSF) in hexagonal Silicon Carbide polytypes have received considerable attention in recent years since it has been found that these defects are responsible for the degradation of forward I-V characteristics in p-i-n diodes. In order to extend the knowledge on these kind of defects and theoretically support experimental findings (specifically, photoluminescence spectral analysis), we have determined the Kohn-Sham electronic band structures, along the closed path Γ-M-K-Γ, using density functional theory. We have also determined the energies of the SSFs with respect to the perfect crystal finding that the (35) and (44) SSFs have unexpectedly low formation energies, for this reason we could expect these two defects to be easily generated/expanded either during the growth or post-growth process steps.
Characterization of Basal Plane Dislocations in 4H-SiC Substrates by Topography Analysis of Threading Edge Dislocations in Epilayers
Authors: Kamata Isaho , Nagano Masahiro , Tsuchida Hidekazu
Published: May 2010

Burgers vector directions of threading edge dislocations (TEDs) in 4H-SiC epitaxial layer are distinguished by grazing incidence high resolution topography. Based on comparison between appearance of KOH etch pits and direction of TED Burgers vector, the size difference of the TED etch pits is found to be dependent on their Burgers vector directions. Examining TEDs in the epilayer by topography, the Burgers vector direction of basal plane dislocations (BPDs) in the substrate is identified. Correspondence between the topography contrast and the sense of a BPD is also investigated.
Optical and Structural Properties of In-Grown Stacking Faults in 4H-SiC Epilayers
Authors: ul Hassan Jawad , Henry Anne , Bergman Peder
Published: May 2010

Two different and novel in-grown triangular stacking faults have been observed and characterized in 4H-SiC epitaxial layers grown on 4o off-cut substrates. The faults were formed at the beginning of the growth and extended continuously in size during the growth. Their structural and optical properties were however different as seen from both synchrotron white beam topography and low temperature photoluminescence. The luminescence spectra were similar but appeared in different energy regions 2.85 – 2.95 eV and 2.48 – 2.64 eV, respectively. BPDs present in the epilayer are found to be transformed into SFs under laser excitation during high resolution optically detected lifetime mapping. The faults are found to expand from the epilayer surface towards the epi-substrate interface. The optical spectrum from this fault is identical to the emission from the single layered Shockley stacking faults with excitonic bandgap of 3.034 eV previously only observed and formed in the bipolar diodes during forward voltage operation.
Condition Dependences of Extended Defect Formation in 4H-SiC by Ion-Implantation/Activation-Anneal Process
Authors: Nagano Masahiro , Tsuchida Hidekazu , Suzuki Takuma , Hatakeyama Tetsuo , Senzaki Junji , Fukuda Kenji
Published: May 2010

Condition dependences of defect formation in 4H-SiC epilayer induced by the implantation/annealing process were investigated using synchrotron reflection X-ray topography and transmission electron microscopy. Nitrogen, phosphorus or aluminum ions were implanted in the 4H-SiC epilayers and then activation annealing was performed. To compare the implantation/annealing process, a sample receiving only the annealing treatment without the implantation was also performed. Two different crucibles (conventional and improved) were used in the annealing process. The formation of single layer Shockley-type stacking faults near the surface was found to have no ion-implantation condition or crucible dependence. The formation of BPD half-loops and the glide of pre-existing BPDs showed clear dependence on the crucibles.
Temperature-Dependence of the Leakage Current of 3C-SiC p+-n Diodes Caused by Extended Defects
Authors: Zippelius Bernd , Krieger M. , Weber Heiko B. , Pensl Gerhard , Nagasawa Hiroyuki , Kawahara Takamitsu , Hatta Naoki , Yagi Kuniaki , Uchida Hidetsugu , Kobayashi Motoki
Published: May 2010

A large leakage current (IR) is observed at reverse bias (VR) in 3C-SiC p+-n diodes. This leakage current is caused by a high density of stacking faults (SFs). The temperature dependence of IR is studied in the temperature range from 100 K to 295 K. It turns out that IR is thermally activated for reverse voltages VR  |170| V. We propose that within this voltage range IR originates from thermally assisted tunneling of electrons and holes from band-like states of the SFs into the conduction and valence band. For VR > |170| V, the thermal barrier is strongly reduced and direct tunneling dominates. These dependences are simulated in the framework of a simplified model.
Room-Temperature Photoluminescence Observation of Stacking Faults in 3C-SiC
Authors: Hirano Rii , Tajima Michio , Itoh Kohei M.
Published: May 2010

We investigated the optical properties of stacking faults (SFs) in cubic silicon carbide by photoluminescence (PL) spectroscopy and mapping. The room-temperature PL spectra consisted of a 2.3 eV peak due to nitrogen and two undefined broad peaks at 1.7 eV and 0.95 eV. On the PL intensity mapping for the 2.3 eV peak, SFs appeared as dark lines. SFs which expose carbon atoms (SFC) and silicon atoms (SFSi) on the surface appeared as bright lines and dark lines, respectively, in PL mapping for the 1.7 eV and 0.95 eV peaks. We believe the two undefined peaks are associated with SFC. This technique allows us to detect SFs nondestructively and to distinguish between SFC and SFSi. We further suggest the presence of inhomogeneous stress around SFCs based on the broadening of the 2.3 eV peak.
A Study of Structural Defects in 3C-SiC Hetero-Epitaxial Films
Authors: Severino Andrea , Anzalone Ruggero , Bongiorno Corrado , La Via Francesco
Published: May 2010

A wide characterization of crystalline defects involved in the 3C-SiC heteroepitaxy on Si is here presented. The aim of this work is to show how analysis techniques, such as transmission electron microscopy (TEM) and x-ray diffraction (XRD), can help the researcher in the study of structural defects. The work is focused on stacking faults and microtwins since both of them influence the atomic stacking along the {111} 3C-SiC planes. Their distinction can indeed be troublesome. It will be shown that TEM can be helpful, by choosing a determined zone axis of observation, for defect characterization and distinction. Moreover, the impact of microtwins on the crystal quality of 3C-SiC films is studied by performing XRD pole figures. By means of this technique and simulations, we found that the <111> direction of the SiC crystal is not aligned to the <110> Si direction, but it is shifted of 3.5° along the <002> Si direction, due to second-order twinnings in the 3C-SiC crystal.
The Formation of Alphabet Lines in 4H SiC after Low-Energy Electron Irradiation
Authors: Steeds John W.
Published: May 2010

Low voltage electron irradiations with electron energies down to the C-displacement threshold have been performed and the irradiated samples studied subsequently by low temperature photoluminescence microscopy. The results were found to depend on the electron energy, the n(N)- or p(Al)-doping and the C- or Si-face irradiated. The implications of these results for the current understanding of the atomic origins of these lines are discussed.
Purifying Mechanism in the Acheson Process - A Thermodynamic Study
Authors: Zhou Li Ying , Telle Rainer
Published: May 2010

To improve the purity of SiC and the yield of high purity SiC in the conventional Acheson Process, the behaviour of metal oxide impurities (Al2O3, CaO, Fe2O3 and MgO) with/without addition of sodium chloride (NaCl) is studied with the help of FactSageTM from a thermodynamic point of view. Equilibrium phases and compositions during evaporation and gas deposition are examined in the system of SiO2 + 3C. The calculation results are compared with industrial observations and published data. Purifying mechanism is clarified for the first time since the invention of the Acheson Process in 1891.
New Lines and Issues Associated with Deep Defect Spectra in Electron, Proton and 4He Ion Irradiated 4H SiC
Authors: Yan Fei , Devaty Robert P. , Choyke Wolfgang J. , Kimoto Tsunenobu , Ohshima Takeshi , Pensl Gerhard , Gali Adam
Published: May 2010

In this paper we revisit sharp low temperature luminescence lines (LTPL) previously generated by high dose 1018 to 1020 cm-2 electron beams in an electron microscope and now produced by low dose 1015 cm-2 electron, 5x1010 cm-2 proton and helium ion irradiation. New no phonon lines E0, F0, θ0, Φ0, K0, G0, J0, M0 and phonon replicas are found. Phonon replicas up to the fifth harmonic are well accounted for by theory giving convincing new evidence that the di-carbon antisite is responsible for these deep defect lines.
Thermal Histories of Defect Centers as Measured by Low Temperature Photoluminescence in n- and p-Type 4H SiC Epilayers Generated by Irradiation with 170 keV or 1 MeV Electrons
Authors: Yan Fei , Devaty Robert P. , Choyke Wolfgang J. , Danno Katsunori , Alfieri Giovanni , Kimoto Tsunenobu , Onoda Shinobu , Ohshima Takeshi , Reshanov Sergey A. , Beljakowa Svetlana , Zippelius Bernd , Pensl Gerhard
Published: May 2010

In this paper we describe an effort to find correlations between low temperature photoluminescence spectroscopy (LTPL) and deep level transient spectroscopy (DLTS) of electron irradiated samples annealed from 25 °C to 1700 °C in 100 °C steps. We report on thermal histories of defect centers created by 170 keV and 1 MeV electron irradiation, as observed by LTPL only. The DLTS results on "twin" samples are presented in a separate paper. Our results indicate that in n-type 4H SiC there is no correlation between the Z1/Z2 center in DLTS and the L1 peak of the DI center seen in LTPL. In p-type 4H SiC we do not find a correlation between a 350 meV DLTS peak above the valence band and the LTPL L1 peak of the DI center. Consequently, we cannot find evidence for a 350 meV ground state postulated in the “Pseudo–Donor” model [3].
A Laterally Resolved DLTS Study of Intrinsic Defect Diffusion in 4H-SiC after Low Energy Focused Proton Beam Irradiation
Authors: Løvlie Lars S. , Vines Lasse , Svensson Bengt Gunnar
Published: May 2010

4H-SiC has been irradiated with 10 keV protons and a laterally resolved DLTS study performed to study the diffusion of irradiation induced intrinsic point defects. It is found that the defects migrate on the order of hundreds of μm laterally and carbon interstitials (CI) are believed to be involved in the defect formation. However, the vertical diffusion lengths are revealed to be several orders of magnitude shorter, on the order of hundreds of nm. Specifically, the Z1,2, S1,2 and EH6,7 levels are found to be generated significant distances from the irradiated area, suggesting that CI or another highly mobile species are involved in the formation of these defects.
Metastable Defects in Low-Energy Electron Irradiated n-Type 4H-SiC
Authors: Beyer Franziska Christine , Hemmingsson Carl G. , Pedersen Henrik , Henry Anne , Isoya Junichi , Morishita Norio , Ohshima Takeshi , Janzén Erik
Published: May 2010

After low-energy electron irradiation of epitaxial n-type 4H-SiC, the DLTS peak
amplitudes of the defects Z1/2 and EH6/7, which were already observed in as-grown layers,
increased and the commonly found peaks EH1 and EH3 appeared. The bistable M-center,
previously seen in high-energy proton implanted 4H-SiC, was detected. New bistable defects,
the EB-centers, evolved after annealing out of the M-center, EH1 and EH3. The reconfiguration
energies for one of the two EB-centers were determined to be about 0.96 eV for both transitions:
from configuration I to II and from configuration II to I. Since low-energy electron irradiation
(<220 keV) affects mainly the carbon atom in SiC, both the M- and EB-centers are likely to
be carbon related defects.
Breakdown of Impurity Al in SiC Polytypes
Authors: Sankin Vladimir Ilich , Averkiev Nikita S. , Monakhov Andrey M. , Shkrebiy Pavel P. , Lepneva Alla A. , Ostroumov Andrey G. , Abramov Pavel L. , Bogdanova Elena V. , Lebedev Sergey P. , Strel'chuk Anatoly M.
Published: May 2010

In this work, we have studied I-V characteristics of Al breakdown in 6H-, 4H- and 15R-SiC in electrical field. As a result there obtained the next original data: 1) decreasing dependence of breakdown field due to the concentration increase in the range of Na – Nd = 5x1017–1019 cm-3; 2) absence of low temperature breakdown when Na - Nd< 1017 cm-3; 3) increasing of breakdown field while temperature declines from 77K to 4.2K; 4) at 300K the breakdown field decreases and the breakdown takes place in samples with the absence of low temperature breakdown; 5) gigantic enhancement of breakdown field at F||C. 6) the theoretical analysis based on the theory of a zero radius potential supports the probability of breakdown field enhancement at F||C.
Detection and Electrical Characterization of Defects at the SiO2/4H-SiC Interface
Authors: Krieger M. , Beljakowa Svetlana , Zippelius Bernd , Afanas'ev Valeri V. , Bauer Anton J. , Nanen Yuichiro , Kimoto Tsunenobu , Pensl Gerhard
Published: May 2010

Two electrical measurement techniques are frequently employed for the characteri-
zation of traps at the SiO2/SiC interface: the thermal dielectric relaxation current (TDRC) and the conductance method (CM). When plotting Dit as a function of the energy position Eit in the bandgap both techniques reveal comparable results for deep interface traps (ECEit > 0:3 eV).
For shallower traps, CM always shows a strong increase of Dit which originates from near interface traps (NIT). TDRC provides a contradictory result, namely a slight decrease of Dit. In this paper, we show that the position of NITs in the oxide close to the interface is responsible for
the invisibility of these traps in TDRC spectra. We further show that NITs become detectable by the TDRC method by using a discharging voltage Vdis close to the accumulation regime.
However, due to the Shockley-Ramo-Theorem the contribution of NITs to the Dit in TDRC spectra is strongly suppressed and can be increased by using thin oxides.
SiC and GaN MOS Interfaces – Similarities and Differences
Authors: Chow T. Paul
Published: May 2010

We have comparatively characterized the electrical characteristics of 4H-SiC and 2H-GaN MOS capacitors and FETs. While progressive refinement of gate oxide processes, notably with NO anneal, has resulted in better threshold voltage control, reduced subthreshold slope and higher field-effect mobility for 4H-SiC MOSFETs, we have recently reported more superior MOS parameters for 2H-GaN MOSFETs. In addition, we have performed MOS-gated Hall measurements to extract the intrinsic carrier concentration and MOS mobility, indicating that both less channel electron trapping and scattering take place in 2H-GaN MOSFETs.
Overview of 3C-SiC Crystalline Growth
Authors: Ferro Gabriel
Published: May 2010

The objective of this review is to set the present state of the art of 3C-SiC crystalline growth by emphasizing the new and promising trends related to this polytype elaboration. The need of high quality 3C seed is showed to be more important than for other polytypes, in order to avoid β→ transformation during high temperature bulk growth. The effect of various parameters, such as supersaturation, gas phase composition, strain or impurities, is discussed. Recent results obtained using vapour-liquid-solid mechanism and continuous feed vapour phase transport are bringing new insight on 3C-SiC stability and setting new standards of material quality.
Systematic Investigation of Interface Properties in 4H-SiC MOS Structures Prepared by Over-Oxidation of Ion-Implanted Substrates
Authors: Okamoto Dai , Yano Hiroshi , Hatayama Tomoaki , Fuyuki Takashi
Published: May 2010

A change in the interface state density in 4H-SiC metal–oxide–semiconductor (MOS) structures by incorporation of various elements was systematically investigated. B, N, F, Al, P, and Cl ions were implanted prior to the oxidation and introduced at the SiO2/SiC interface by subsequent thermal oxidation. Interface state density near the conduction band edge for Al-, B-, F-, and Cl-implanted MOS capacitors increased with implantation dose. On the other hand, a strong reduction of the interface state density was observed for N- and P-implanted samples when the implantation dose was larger than 5.0 × 1012 cm−2. It was found that the interface state density can be reduced by P as well as N.
Improved Electrical Properties of SiC-MOS Interfaces by Thermal Oxidation of Plasma Nitrided 4H-SiC(0001) Surfaces
Authors: Kagei Yusuke , Kirino Takashi , Watanabe Yuu , Mitani Shuhei , Nakano Yuki , Nakamura Takashi , Hosoi Takuji , Shimura Takayoshi , Watanabe Heiji
Published: May 2010

We propose a treatment of nitrogen radical irradiation to 4H-SiC surfaces for improving thermally grown SiO2/SiC interfaces. X-ray photoelectron spectroscopy (XPS) analyses revealed that a 1.7-nm-thick nitride film was formed by nitrogen radical exposure for 30 min and that Si-N bonds were retained after subsequent 10 min oxidation. It was also confirmed by secondary ion mass spectrometry (SIMS) that nitrogen atoms were piled up at the SiO2/SiC interface for the samples fabricated by thermal oxidation for 3 min with nitrogen plasma exposure. The metal-oxide-semiconductor (MOS) capacitors with a thin oxynitride layer formed by nitrogen radical exposure to the SiC surface and subsequent thermal oxidation exhibited excellent capacitance-voltage (C-V) characteristics. The interface state density (Dit) was significantly reduced by nitrogen radical exposure even at the shallow energy level near the conduction band edge. A minimum Dit value of 1.4 × 1011 cm-2eV-1 at Ec – E = 0.44 eV was achieved. Therefore, we can conclude that the treatment of nitrogen radical irradiation to the SiC surface prior to thermal oxidation is a promising method for improving SiC-MOS characteristics.
Investigation of Oxide Films Prepared by Direct Oxidation of C-Face 4H-SiC in Nitric Oxide
Authors: Okamoto Dai , Yano Hiroshi , Oshiro Yuki , Hatayama Tomoaki , Uraoka Yukiharu , Fuyuki Takashi
Published: May 2010

Characteristics of metal–oxide–semiconductor (MOS) capacitors and MOS field-effect transistors (MOSFETs) fabricated by direct oxidation of C-face 4H-SiC in NO were investigated. It was found that nitridation of the C-face 4H-SiC MOS interface generates near-interface traps (NITs) in the oxide. These traps capture channel mobile electrons and degrade the performance of MOSFETs. The NITs can be reduced by unloading the samples at room temperature after oxidation. It is important to reduce not only the interface states but also the NITs to fabricate high-performance C-face 4H-SiC MOSFETs with nitrided gate oxide.
Electrical Properties and Gas Sensing Characteristics of the Al2O3/4H SiC Interface Studied by Impedance Spectroscopy
Authors: Sobas Pawel A. , Nilsen Ola , Fjellvåg Helmer , Svensson Bengt Gunnar
Published: May 2010

Using impedance spectroscopy (IS) for characterization of the electrical properties and gas sensing characteristics of Al2O3/4H-SiC (MOS) structures, insight on the capacitive and resistive contributions in the interfacial region of the MOS structures is obtained. Applying DC bias voltages between accumulation and depletion (corresponding to the interfacial region) allows investigation of the voltage shift of the capacitance versus voltage (CV) curve at different temperatures and atmospheres. This voltage shift forms the basis to use the MOS structure as a gas sensor. The MOS capacitance, as extracted from IS data, is different from the one obtained using CV measurements, due to the ability of distinguishing the resistive contribution (using IS). Voltage shifts between 1 and 2 V are clearly revealed during exposure to hydrogen and oxygen, and this shift exhibits a long-term stability of operation at temperatures up to 500°C. Hence, Al2O3 exhibits great promise as a gate dielectric in MOS-based gas detecting devices for use at elevated temperatures.
Experimental Verification of the Cluster Effect on Giant Step Bunching on 4H-SiC (0001) Surfaces
Authors: Ishida Yuuki , Takahashi Tetsuo , Okumura Hajime , Arai Kazuo , Yoshida Sadafumi
Published: May 2010

In this study, we investigated the cluster effect on the occurrence of giant step bunching. We generated carbon clusters on 4H-SiC (0001) surfaces by thermal decomposition of SiC in an Ar atmosphere and controlled the surface concentrations of the clusters by adding H2 gas. We found the boundaries between surfaces with and without giant steps to show Arrhenius-type behavior. This behavior agreed with our predictions deduced from a chemical reaction model that takes the cluster effect into account, suggesting that giant step bunching is attributable to the formation of clusters on SiC.
Study of the Spontaneous Nucleation of 3C-SiC Single Crystals Using CF-PVT Technique
Authors: Galben-Sandulache Irina G. , Sun Guoli L. , Dedulle Jean Marc , Ouisse Thierry , Madar Roland , Pons Michel , Chaussende Didier
Published: May 2010

The control of the nucleation step is a critical issue for a future development of 3C-SiC bulk growth. The possibility to get very high quality 3C-SiC single crystal through self-nucleation on graphite was already demonstrated but the large number of nuclei limits the growth of only one crystal. In this study, we have investigated different configurations that help improving the nucleation step. For that, the “necking” stage, well established in Bridgman or Czochralski growth processes, has been successfully applied to the growth of 3C-SiC with the CF-PVT technique. This has allowed getting only one 3C-SiC crystal. The enlarged parts, after having passed the neck, are of high structural quality.
Single Shockley Faults Enlargement during Micro-Photoluminescence Defects Mapping
Authors: Canino Andrea , Camarda Massimo , La Via Francesco
Published: May 2010

Single Shockley faults have been studied in 4H-SiC epitaxial layers by using a spatial resolved micro-photoluminescence technique. In particular the Effect of the UV pumping laser has been investigated. We demonstrated that high power density exposition at 325 nm affects drastically the structural properties of the epitaxial layers leading to a growth of this defect. We also demonstrated that by opportunely tuning the power density of the UV laser on the sample it is possible to analyze a wide area without producing any negative effect.
Novel Fabrication Technology for Devices with nearly Temperature-Independent Forward Characteristics
Authors: Heim Sandra , Albrecht Andreas , Bartsch Wolfgang
Published: May 2010

In this work we discuss a structure of a p-doped Poly-Si layer and a Ni layer deposited onto n-type 4H-SiC in order to form a Schottky-like contact which undergoes a specific temperature budget to establish a temperature independent forward characteristic of the formed rectifying junction. The results of our treatment is discussed in terms of a hetero junction, though temperature treated NiSi-layers normally are expected to show an ohmic behavior.
Is the Liquid Phase a Viable Approach for Bulk Growth of 3C-SiC?
Authors: Mercier Frédéric , Kim-Hak Olivier , Lorenzzi Jean , Dedulle Jean Marc , Ferro Gabriel , Chaussende Didier
Published: May 2010

Despite outstanding properties, the development of 3C-SiC electronics is still suffering from the lack of bulk 3C-SiC substrates. Up to now, there is no real seed and optimized growth processes for this material. We address in this work the bulk growth of 3C-SiC by a two-step-liquid phase approach. By coupling experiments with global process simulation, we address the problems that must be overcome to consider the solution growth technique as a possible approach for the growth of bulk 3C-SiC.
Investigations on Surge Current Capability of SiC Schottky Diodes by Implementation of New Pad Metallizations
Authors: Hilsenbeck Jochen , Treu Michael , Rupp Roland , Rüschenschmidt Kathrin , Kern Ronny , Holz Matthias
Published: May 2010

In this paper we describe how a merged pn Schottky diode (MPS diode) is capable to drive surge current levels far beyond the normal current of the diode and how to improve the device in order to achieve even higher surge current levels. For a sine half wave of 10 µs an 8A MPS diode (size: 2.52mm2) with conventional Al pad metallization shows surge current levels of greater than 500A, using Cu it can be increased to ~900A. For 10ms pulse length a different behaviour was observed, here diodes with Al pad metallization show a higher surge current level (80A) compared to Cu pad metallization (~ 40A). The root cause for this negative result at longer pulse time is based in a chemical interaction between Cu and the Schottky metal (Ti). Additionally, an outlook is given how Cu can contribute to improved surge current capability also at longer pulse lengths.
Manganese in 4H-SiC
Authors: Linnarsson Margareta K. , Audren Aurégane , Hallén Anders
Published: May 2010

Manganese diffusion in 4H-SiC for possible spintronic applications is investigated. Ion implantation is used to introduce manganese in n-type and p-type 4H-SiC and subsequent heat treatment is performed in the temperature range of 1400 to 1800 °C. The depth distribution of manganese is recorded by secondary ion mass spectrometry and Rutherford backscattering spectrometry in the channeling direction is employed for characterization of crystal disorder. After the heat treatment, the crystal order is improved and a substantial rearrangement of manganese is revealed in the implanted region. However, no pronounced manganese diffusion deeper into the sample is recorded.
Effects of Implantation Temperature on Sheet and Contact Resistance of Heavily Al Implanted 4H-SiC
Authors: Watanabe Tomokatsu , Aya Sunao , Hattori Ryo , Imaizumi Masayuki , Oomori Tatsuo
Published: May 2010

Effects of implantation temperature on electrical properties of heavily-Al-doped 4H-SiC layer formed with Al implantation have been investigated. To form the p++ 4H-SiC with the original 4H-stacking structure, the implantation temperature above 175 °C is needed. A decrease in the implantation temperature below 250 °C leads to an increase in the NA-ND. It is suggested that an increase in the density of vacancies with a decrease in the implantation temperature promotes the Al substitution to lattice sites during activation annealing. The lower-temperature implantation also causes a decrease in activation energy for the p-type electrical conduction and a decrease in p-type ohmic contact resistivity. We presume that the increase in the Al acceptors at low-implantation temperatures gives expansion of the impurity bands and formation of valence band tail-states, causing the decrease in the impurity binding energy. The properties obtained with the lower-temperature implantation are desirable for practical applications especially at low temperatures.
Reactive-Ion-Etching Induced Deep Levels Observed in n-Type and p-Type 4H-SiC
Authors: Kawahara Koutarou , Alfieri Giovanni , Krieger M. , Kimoto Tsunenobu
Published: May 2010

In this study, deep levels are investigated, which are introduced by reactive ion etching (RIE) of n-type/p-type 4H-SiC. The capacitance of as-etched p-type SiC is remarkably small due to compensation or deactivation of acceptors. These acceptors can be recovered to the initial concentration of the as-grown sample after annealing at 1000oC. However, various kinds of defects remain at a total density of ~5× 1014 cm-3 in a surface-near region from 0.3 μm to 1.0 μm even after annealing at 1000oC. The following defects are detected by Deep Level Transient Spectroscopy (DLTS): IN2 (EC – 0.35 eV), EN (EC – 1.6 eV), IP1 (EV + 0.35 eV), IP2 (HS1: EV + 0.39 eV), IP4 (HK0: EV + 0.72 eV), IP5 (EV + 0.75 eV), IP7 (EV + 1.3 eV), and EP (EV + 1.4 eV). These defects generated by RIE can be significantly reduced by thermal oxidation and subsequent annealing at 1400oC.
Hexagonality and Stacking Sequence Dependence of Etching Properties in Cl2-O2-SiC System
Authors: Hatayama Tomoaki , Koketsu Hidenori , Yano Hiroshi , Fuyuki Takashi
Published: May 2010

Thermal etching of hexagonal (4H-, 6H-, 8H- and 10H-), rhombohedral (15R- and 21R-), and cubic (3C-) SiC Si-faces was performed between 900 and 1000oC in a mixed gas of chlorine (Cl2) and oxygen (O2). In the case of well oriented Si-faces, the 3C-SiC (111) substrate was etched fastest in polytypes. The etching rate in the dislocation-free area depended on the hexagonality. Etch pits with definite shapes appeared, which depend on the type of dislocation and crystal structures. On the basis of these results, etching properties are discussed.
Self-Formation of Specific Pyramidal Planes in 4H-SiC Formed by Chlorine Based Ambience
Authors: Koketsu Hidenori , Hatayama Tomoaki , Amijima K. , Yano Hiroshi , Fuyuki Takashi
Published: May 2010

. 　 Crystallographically specific pyramidal planes in 4H-SiC could be naturally formed at mesa sidewalls by a thermal etching at 900oC in a chlorine (Cl2) based ambience. The mesa structures have been fabricated on the 4H-SiC C-face with 0-45o off-angle toward [11-20]. The etched surface was rather smooth, and bunched step structures on the specific pyramidal planes were not observed with atomic force and scanning electron microscopes. The formation mechanisms of the specific pyramidal planes at mesa sidewalls are discussed on the basis of these experimental results.
Property Modification of 3C-SiC MEMS on Ge-Modified Si(100) Substrates
Authors: Niebelschütz Florentina , Zhao Wei Hong , Brueckner Klemens , Tonisch Katja , Linß Matthias , Hein Matthias A. , Pezoldt Joerg
Published: May 2010

The manipulation of nucleation and growth conditions with Ge deposition prior to the carbonization and epitaxial growth changes the residual stress and the material quality of 3C-SiC(100)-layers grown on Si(100). This enables the modification of quality factor and resonant frequency of microelectromechanical systems (MEMS) based on 3C-SiC-layers. Measured resonant frequencies and quality factors of the magnetomotively actuated MEMS exhibit a dependence on the Ge amount at the interface of the Si/SiC heterostructure. This offers a degree of freedom to adjust the MEMS properties within a certain range to the requirements necessary for specific applications. The observed dependencies of the Young’s modulus are in good agreement with the trends of residual stress and Young’s modulus, which were determined on as grown 3C-SiC(100):Ge samples by fourier transform infrared (FTIR) spectroscopy and nanoindentation.
Residual Stress Measurement and Simulation of 3C-SiC Single and Poly Crystal Cantilevers
Authors: Anzalone Ruggero , Camarda Massimo , Alquier Daniel , Italia M. , Severino Andrea , Piluso Nicolò , La Magna Antonino , Foti Gaetano , Locke Christopher , Saddow Stephen E. , Roncaglia Alberto , Mancarella Fulvio , Poggi Antonella , D'Arrigo Giuseppe , La Via Francesco
Published: May 2010

The fabrication of SiC MEMS-based sensors requires new processes able to realize microstructures on either bulk material or on the SiC surface. The hetero-epitaxial growth of 3C-SiC on silicon substrates allows one to overcome the traditional limitations of SiC micro-fabrication. In this work a comparison between single crystal and poly crystal 3C-SiC micro-machined structures will be presented. The free-standing structures realized (cantilevers and membrane) are also a suitable method for residual field stress investigation in 3C-SiC films.
Measurement of the Raman shift indicates that the mono and poly-crystal 3C-SiC structures release the stress in different ways. Finite element analysis was performed to determine the stress field inside the films and provided a good fit to the experimental data. A comprehensive experimental and theoretical study of 3C-SiC MEMS structures has been performed and is presented.
Fabrication of 1.2kV, 100A, 4H-SiC(0001) and (000-1) Junction Barrier Schottky Diodes with Almost Same Schottky Barrier Height
Authors: Kinoshita Akimasa , Ohyanagi Takasumi , Yatsuo Tsutomu , Fukuda Kenji , Okumura Hajime , Arai Kazuo
Published: May 2010

It is known that a Schottky barrier height (b) of metal/C-face 4H-SiC Schottky barrier diode (SBD) differ from b of metal/Si-face 4H-SiC SBD. Furthermore, b of metal/4H-SiC SBD varies with annealing temperature. We fabricate 0.231mm2 SBD with Ti/SiC interface using Si-face and C-face 4H-SiC. These SBDs are annealed at several temperatures after a formation of the Ti/SiC interface. As a result, b of Ti/C-face 4H-SiC interface annealed at 400 oC is nearly equal to b of Ti/Si-face 4H-SiC interface annealed at 500 oC and the n-values of these SBDs are nearly equal to the ideal value (unity). Using that annealing condition, we fabricated 25mm2 junction barrier Schottky (JBS) diodes with Ti/SiC interface on Si-face and C-face 4H-SiC epitaxial substrate. b of Si-face and C-face JBS diodes are 1.26eV and 1.24eV, respectively. The leakage currents for both Si-face and C-face JBS diodes are less than 1mA/cm2. The current of 100A is obtained at the forward bias voltage of 1.95V and 2.16V for the Si-face JBS and the C-face JBS.
4.6 kV, 10.5 mOhm×cm2 Nickel Silicide Schottky Diodes on Commercial 4H-SiC Epitaxial Wafers
Authors: Vassilevski Konstantin , Nikitina Irina P. , Horsfall Alton B. , Wright Nicolas G. , Johnson C. Mark
Published: May 2010

4H-SiC diodes with 0.60 mm2 nickel silicide Schottky contacts were fabricated on commercial epitaxial layers. At room temperature, the diodes have specific on-resistances (RON-SP) down to 10.5 mΩcm2 and blocking voltages (VBL) up to 4.6 kV, which is equal to 93 % of the calculated parallel plane breakdown voltage for used epitaxial structure. The corresponding figure-of-merit, defined as (VBL)2/RON-SP, is equal to 2015 MW/cm2 and is among the highest FOM values reported to date. The diodes demonstrated stable operation at forward current of 1 A and VBL value in excess of 3.3 kV at ambient temperatures up to 200 °C.
Radiation Hardness Evaluation of SiC-BGSIT
Authors: Tanaka Yasunori , Onoda Shinobu , Takatsuka Akio , Ohshima Takeshi , Yatsuo Tsutomu
Published: May 2010

In this study, we evaluated the radiation hardness of SiC Buried Gate Static Induction Transistors (SiC-BGSITs) and Si-based switching devices up to the absorbed dose of 10 MGy(SiO2). The on-voltage Von of Si-IGBT degraded excessively at the early stage of the irradiation (>~0.1 MGy(SiO2)) due to the bulk damage produced by Compton electrons like the gain degradation in Si bipolar transistors. The threshold voltage Vth of Si-MOSFET was very sensitive against the radiation due to the competing mechanism between the generation of the hole traps in the gate SiO2 and the SiO2/Si interface states. Moreover, the breakdown voltage VBR and leak current Ileak of MOSFET degraded significantly against the absorbed dose. While, the electrical properties of SiC-BGSIT was very stable even after the irradiation of 10 MGy(SiO2).
Amplitude Shift Keyed Radio Communications for Hostile Environments
Authors: Brennan Daniel , Miao Bing , Vassilevski Konstantin , Wright Nicolas G. , Horsfall Alton B.
Published: May 2010

This work presents the amplitude modulation radio transmission system for communications in hostile environments. The commissioning of a high temperature oscillator and AM mixer system for the purpose of Amplitude Shift Keyed modulation is presented. While previous work has demonstrated oscillators in the Ultra High Frequency (UHF) band, these have been targeted at applications such as radar and mobile telephones. In this paper we have concentrated on the shortwave bands to maximize the range between a sensor unit and the receiver within wireless networks. The work demonstrates that simple communication systems are already possible for hostile environments and allow for simple sensor data to be wirelessly transmitted to safer working areas.
Minimization of Drain-to-Gate Interaction in a SiC JFET Inverter Using an External Gate-Source Capacitor
Authors: Berry Olivier , Hamieh Youness , Raël Stéphane , Meibody-Tabar Farid , Vieillard Sébastien , Bergogne Dominique , Morel Hervé
Published: May 2010

This paper presents a study on a SiC JFET leg of a 3-leg Voltage Source Inverter (VSI). The switching curves obtained with the JFET working in free wheeling mode are shown to point out drain-to-gate interaction effects. Indeed, during the drain-source voltage variations, the JFET gate-source voltage can have considerable variations, because of the electrical coupling induced by the gate-drain capacitance Cgd. When the gate-source voltage variation becomes too negative, there is a risk of occurrence of the phenomenon of punch-through in the gate-source junction. Conversely, when it is enough positive, the JFET may conduct and lead to a leg short-circuit. To decrease these undesired effects for the JFET legs and consequently for the SiC JFET inverter, an external gate-source capacitor is used. This solution is studied and optimized by simulation on an inverter leg.
Circuit Modeling of Vertical Buried-Grid SiC JFETs
Authors: Tolstoy Georg , Peftitsis Dimosthenis , Lim Jang Kwon , Bakowski Mietek , Nee Hans Peter
Published: May 2010

The main problem when the conventional PSpice JFET model is used to simulate a vertical short-channel buried-grid JFET is caused by the constant values of Threshold Voltage (VTO) and Transconductance (BETA). This paper presents a new model for the vertical short-channel buried-grid 1200V JFET, where both VTO and BETA vary with respect to the Drain-Source voltage. Simulation data from Medici have been analyzed in order to extract the analytical equations for VTO and BETA. Also other PSpice parameters are extracted from these data. The proposed circuit model has been simulated in Matlab by optimizing the same algorithm that PSpice uses. A variety of results are shown and discussed in this paper.
1360 V, 5.0 mΩcm2 Double-Implanted MOSFETs Fabricated on 4H-SiC(000-1)
Authors: Kono Hiroshi , Suzuki Takuma , Mizukami Makoto , Ota Chiharu , Harada Shinsuke , Senzaki Junji , Fukuda Kenji , Shinohe Takashi
Published: May 2010

Silicon carbide Double-Implanted Metal-Oxide-Semiconductor Field-Effect Transistors (DIMOSFETs) were fabricated on 4H-SiC (000-1) carbon face. The DIMOSFETs were characterized from room temperature to 250°C. At room temperature, they showed a specific on-resistance of 4.9 mΩcm2 at a gate bias of 20 V and a drain voltage of 1.0 V. The specific on-resistance taken at a drain current (Id) of 260 A/cm2 was 5.0 mΩcm2. The blocking voltage of this device was higher than 1360 V at room temperature. At 250°C, the specific on-resistance increased from 5.0 mΩcm2 to 12.5 mΩcm2 and the threshold voltage determined at Id = 26 mA/cm2 decreased from 5.5 V to 4.3 V.
4H-SiC Homoepitaxial Growth on Vicinal-Off Angled Si-Face Substrate
Authors: Kojima Kazutoshi , Ito Sachiko , Senzaki Junji , Okumura Hajime
Published: May 2010

We have carried out detailed investigations of 4H-SiC homoepitaxial growth on vicinal off-angled Si-face substrates. We found that the surface morphology of the substrate just after in-situ H2 etching was also affected by the value of the vicinal-off angle. Growth conditions consisting of a low C/Si ratio and a low growth temperature were effective in suppressing macro step bunching at the grown epilayer surface. We also demonstrated epitaxial growth without step bunching on a 2-inch 4H-SiC Si-face substrate with a vicinal off angle of 0.79o. Ni Schottky barrier diodes fabricated on an as-grown epilayer had a blocking voltage above 1000V and a leakage current of less than 5x10-7A/cm2. We also investigated the propagation of basal plane dislocation from the vicinal off angled substrate into the epitaxial layer.
Improved Characteristics of 4H-SiC MISFET with AlON/Nitrided SiO2 Stacked Gate Dielectrics
Authors: Hosoi Takuji , Kagei Yusuke , Kirino Takashi , Watanabe Yuu , Kozono Kohei , Mitani Shuhei , Nakano Yuki , Nakamura Takashi , Watanabe Heiji
Published: May 2010

We investigated the impact of a combination treatment of nitrogen plasma exposure and forming gas annealing (FGA) for a thermally grown SiO2 layer on channel electron mobility in 4H-SiC metal-insulator-semiconductor field-effect-transistors (MISFETs) with and without deposited aluminum oxynitride (AlON) overlayers. This treatment was effective for improving the interface properties of nitrided SiO2/SiC structures formed by thermal oxidation in NOx ambient as well as pure SiO2/SiC structures. A channel mobility enhancement was perfectly consistent with a reduction in interface state density depending on the process conditions of the combination treatment, and a peak mobility of 26.9 cm2/Vs was achieved for the MISFETs with the nitrided SiO2 single dielectric layer. Comparable channel mobility was obtained with a gate insulator consisting of the AlON stacked on a thin nitrided SiO2 interlayer, indicating that both the combination treatment and the AlON/SiO2 stacked dielectrics can be integrated into the SiC MISFET fabrication processes.
Effect of Doping Concentration in Buried-Channel NMOSFETs on Electrical Properties of 4H-SiC CMOS Devices
Authors: Okamoto Mitsuo , Iijima Miwako , Yatsuo Tsutomu , Fukuda Kenji , Okumura Hajime
Published: May 2010

We fabricated 4H-silicon carbide (SiC) Complementary Metal-Oxide-Semiconductor (CMOS) devices with wet gate oxidation processing. The channel properties of n-channel MOS Field-Effect-Transistor (NMOS) were controlled by buried channel (BC) structure. The electrical properties of CMOS devices depended on the doping concentration of the BC-layer (Nbc) for NMOS. The SiC CMOS inverters with high Nbc indicated fast operation at the delay time (Td) of 4.8 ns for supply voltage of 15 V. To our knowledge, Td obtained in this study is the smallest among the reported values for SiC CMOS inverters.