bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of 3C-SiC Lateral Growth on 4H-SiC Mesas
Authors: Lorenzzi Jean , Jegenyes Nikoletta , Lazar Mihai , Tournier Dominique , Cauwet François , Carole Davy , Ferro Gabriel
Published: March 2011

In this work we report on 3C-SiC heteroepitaxial growth on 4H-SiC(0001) substrates which were patterned to form mesa structures. Two different deposition techniques were used and compared: vapour-liquid-solid (VLS) mechanism and chemical vapour deposition (CVD). The results in terms of surface morphology evolution and the polytype formation using these growth techniques were studied and compared. It was observed both 4H lateral growth from the mesa sidewalls and 3C enlargement on top of the mesas, the former being faster with CVD and VLS. Only VLS technique allowed elimination of twin boundaries for proper orientation of the mesa sidewalls.
Growth of 4H- and 3C-SiC Epitaxial Layers on 4H-SiC Step-Free Mesas
Authors: Myers-Ward Rachael L. , Nyakiti Luke O. , Hite Jennifer K. , Glembocki Orest J. , Bezares Francisco J. , Caldwell Joshua D. , Imhoff Eugene A. , Hobart Karl D. , Culbertson James C. , Picard Yoosuf N. , Wheeler Virginia D. , Eddy Charles R. , Gaskill D. Kurt
Published: March 2011

Homo- and heteroepitaxial 3C-SiC layers were grown on 4H-SiC step-free mesas. The yields of smooth, defect-free mesas were ~ 17% for both intentionally and unintentionally doped films, while those with screw dislocations and multiple stepped surfaces were ~ 22%. The electronic and structural properties of the mesas were found on a micrometer-sized length scale using µ-PL and µ-Raman, respectively. 3C-SiC mesas were found to have complete 3C-SiC coverage with some of the mesas having electronic defects, while other mesas were found to be defect-free.
On Application of Sublimation Epitaxy to Growth of Bulk 3C-SiC Crystals
Authors: Lebedev Alexander A. , Abramov Pavel L. , Zubrilov A.S. , Bogdanova Elena V. , Lebedev Sergey P. , Seredova Natasha V. , Tregubova Alla S.
Published: March 2011

It is demonstrated that polytype-homogeneous, thick (>100 m) epitaxial 3C-SiC layers of good quality with diameters of no less than 25 mm can be grown on 6H-SiC substrates by sublimation epitaxy in vacuum. These layers can be used as seeds for growing bulk 3C-SiC crystals by modified Lely method.
Evaluation of Curvature and Stress in 3C-SiC Grown on Differently Oriented Si Substrates
Authors: Watts Bernard Enrico , Attolini Giovanni , Besagni Tullo , Bosi Matteo , Ferrari Claudio , Rossi Francesca , Riesz Ferenc , Jiang Liu Di
Published: March 2011

To assess deformation issues in SiC/Si, different pre-growth procedures were investigated, involving the addition of SiH4 to C3H8 during the temperature ramps used for the carbonization. 3C-SiC layers were deposited on (001) and (111) Si substrates by VPE. The mechanical deformation of the wafer was measured by makyoh, obtaining 2D maps of the entire wafers. For the same pre-growth procedures, the substrate curvature depends strongly on the orientation of the substrate, (001) or (111), being generally lower for (111) substrates. The deformation results were compared with XRD and Raman spectroscopy. Plastic deformation of the substrate was evidenced by XRD, while the presence of tensile stress is suggested by Raman analysis.
A Comparative Study of the Morphologies of Etch Pits in Semi-Insulating Silicon Carbide Single Crystals
Authors: Peng Yan , Xu Xian Gang , Hu Xiao Bo , Chen Xiu Fang , Gao Yu Qiang
Published: March 2011

Contactless resistivity mapping, scanning electron microscope (SEM) and confocal laser microscope have been used to study the relationship of the resistivity and the etching behavior of the semi-insulating 6H-SiC wafer. Evidence is presented that the morphologies of the etch pits vary significantly with the impurity concentrations. The V impurity strongly affects the etch rates of edge, screw and mixed dislocations. For the dislocation containing the Burgers vector component of <0001>, its vertical etch rate is enhanced distinctly. In contrast, the horizontal etch rate becomes larger for the dislocation containing the Burgers vector component of < >. The shape of the etch pits reflects the Fermi level of the semi-insulating wafer and the net shallow impurity concentration.
Electrical Parameters of Bulk 3C-SiC Crystals Determined by Hall Effect, Magnetoresistivity, and Contactless Time-Resolved Optical Techniques
Authors: Ščajev Patrik , Mekys A. , Malinovskis P. , Storasta Jurgis , Kato Masashi , Jarašiūnas Kęstutis
Published: March 2011

The electrical and optical techniques have been applied for investigation of carrier transport and recombination features in thick free-standing 3C-SiC layers. Temperature dependencies of Hall mobility, magneto-resistivity, and conductivity indicated presence of high potential barriers, up to 0.4 eV. The carrier mobilities and equilibrium densities were calculated in the barrier and inter-barrier regions. Contactless measurements of the excess carrier ambipolar mobility and lifetime at 1016-18 cm-3 injection levels revealed carrier scattering solely by phonons in 80 – 800 K range. A correlation between the temperature dependencies of carrier lifetime and ambipolar mobility pointed out that diffusion-limited surface recombination at extended defects contributes significantly to the carrier lifetime.
Carrier Dynamics in Hetero- and Homo-Epitaxially Sublimation Grown 3C-SiC Layers
Authors: Manolis Georgios , Beshkova Milena , Syväjärvi Mikael , Yakimova Rositza , Jarašiūnas Kęstutis
Published: March 2011

We investigated non-equilibrium carrier dynamics in ~20μm thick 3C-SiC layers, grown by sublimation epitaxy directly on 6H-SiC substrate or buffered by a 3C seed layer. Differential transmission and light-induced transient grating techniques were applied to determine the ambipolar diffusion coefficient, carrier lifetime, and thermal activation energy of defects. The temperature dependences of ambipolar mobility and lifetime in 80-700 K range revealed the carrier scattering processes as well the impact of defects on the recombination rate, thus indicating slightly improved photoelectrical parameters of the homoepitaxially grown 3C layer. The determined thermal activation energies of 35 and 57 meV were attributed to the nitrogen impurity.
Structural and Optical Investigation of VLS Grown (111) 3C-SiC Layers on 6H-SiC Substrates in Sn-Based Melts
Authors: Marinova Maya , Mantzari Alkyoni , Sun Jian Wu , Lorenzzi Jean , Andreadou Ariadne , Zoulis Georgios , Juillaguet Sandrine , Ferro Gabriel , Camassel Jean , Polychroniadis Efstathios K.
Published: March 2011

The current communication focuses on the investigation of 3C-SiC layers grown by the Vapour-Liquid-Solid mechanism on on-axis Si-face 6H-SiC substrates in SiSn melts with different compositions and at different growth temperatures. The layers are studied by Transmission Electron Microscopy and Low Temperature Photoluminescence. It was found that for melts with Sn concentration higher than 60 at% large Sn-related precipitates are formed. The depth distribution of the Sn precipitates strongly depends not only on the melt composition but also on the growth temperature. Their formation strongly influences the stacking fault density and the dopant incorporation in the layers. Lower Sn concentrations combined with higher growth temperatures should result in 3C-SiC layer with enhanced structural quality.
Examination of Two P-Type 4H SiC Samples Having Similar Resistivity but Very Different Radiation Damage and Annealing Characteristics
Authors: Steeds John W.
Published: March 2011

In the course of studying by low temperature photoluminescence spectroscopy a wide range of electron-irradiated samples of p(Al)-type epitaxial layers of 4H SiC, from a variety of different sources of supply, the results were found to fit into two very different categories. The origin of these differences has been explored using a wide range of experimental techniques and found to result from the degree of compensation of the aluminium by nitrogen in the layers. Nitrogen concentrations deduced by SIMS experiments on these materials were found to be unreliable. The two different categories of material, called V and AB here, showed marked differences in their subsequent annealing behaviour and the implications of this distinction are discussed.
Uniformity of Properties of 4H-SiC CVD Films under Exposure to Radiation
Authors: Ivanov Alexander M. , Strokan Nikita B. , Scherbov N.A. , Lebedev Alexander A.
Published: March 2011

Non-uniformities of electrical properties of 4H-SiC CVD films have been revealed using physico-chemical reactions occurring upon introduction of radiation-induced structural defects. Primary knocked-out atoms and vacancies actively interact with defects of the starting material and thereby form the final system of radiation centers. The samples were irradiated with 900 keV electrons and 8 MeV protons at doses not leading to conductivity compensation ( 7.5  1012 cm–2) and a dose of 6  1014 cm–2 causing deep compensation. Capacitance methods demonstrated that characteristics of samples ~3 mm in size are not identical. The nuclear spectrometry technique, which enables microprobing of samples, demonstrated individual behavior of separate parts of a film with areas of tens of square micrometers (the dimension of α-particles track cross-section).
Reduction in Majority-Carrier Concentration in Lightly-Doped 4H-SiC Epilayers by Electron Irradiation
Authors: Matsuura Hideharu , Yanagisawa Hideki , Nishino Kozo , Nojiri Takunori , Onoda Shinobu , Ohshima Takeshi
Published: March 2011

The mechanisms for the reduction in the hole concentration in lightly Al-doped p-type 4H-SiC epilayers by electron irradiation as well as in the electron concentration in lightly N-doped n-type 4H-SiC epilayers by electron irradiation are investigated. In the p-type 4H-SiC epilayers, the temperature dependence of the hole concentration, , is not changed by 100 keV electron irradiation, while the is decreased by 150 keV electron irradiation. The density of Al acceptors with energy level eV decreases with increasing fluence of 150 keV electrons, whereas the density of deep acceptors with energy level eV increases. In the n-type 4H-SiC epilayers, the temperature dependence of the electron concentration, , is decreased by 200 keV electron irradiation. The density of N donors located at hexagonal C-sublattice sites decreases significantly with increasing fluence of 200 keV electrons, whereas the density of N donors located at cubic C-sublattice site decreases slightly.
On the Quantification of Al Incorporated in SiC Material Using Particle Induced X-Ray Emission Technique
Authors: Soueidan Maher , Nsouli Bilal , Ferro Gabriel , Younes Ghassan
Published: March 2011

In this work the capability of the proton induced X-ray emission (PIXE) technique to monitor a rapid, non-destructive and accurate quantification of Al on and in Si-based matrix is discussed. Optimization of PIXE acquisition parameters was performed using as reference a thin Al film (2.5 nm) thermally evaporated onto silicon substrate. In order to improve the sensitivity for Al detection and quantitative determination, a systematic study was undertaken using proton ion beam at different energies (from 0.3 to 3 MeV) with a different tilting angle (0°, 60°, and 80°). The limit of detection (LOD) was found to be lower than 0.2 nm. The optimum PIXE conditions (energy, angle) were applied for determining the Al doping concentration in thin (1 µm) 4H-SiC homoepitaxial layer. The Al concentration as determined by PIXE was found to be 3.9x1020 at/cm3 in good agreement with SIMS measurements, and the LOD was estimated to be 6x1018 at/cm3.
Evaluation of Long Carrier Lifetimes in Very Thick 4H-SiC Epilayers
Authors: Miyazawa Tetsuya , Ito Masahiko , Tsuchida Hidekazu
Published: March 2011

We investigate the carrier lifetimes in very thick 4H-SiC epilayers (~250 μm) by means of time-resolved photoluminescence and microwave photoconductive decay. Both the minority carrier lifetime and the high injection lifetime are found to reach 18.5 μs by applying the carbon implantation/annealing method to the as-grown epilayers. We also study the epilayer thickness dependence of the carrier lifetime by successive experiments involving lifetime measurement and polishing. Based on the relationships between epilayer thickness and carrier lifetime, the bulk carrier lifetime and the hole diffusion constant are discussed.
Quality Investigation of 3C-SiC Crystals Grown by CF-PVT Technique
Authors: Galben-Sandulache Irina G. , Marinova Maya , Mantzari Alkyoni , Sun Guoli L. , Andreadou Ariadne , Chaussende Didier , Polychroniadis Efstathios K.
Published: March 2011

This work presents the crystalline quality investigation of 3C-SiC unseeded crystals grown from vapor phase. Samples were polished after different crystallographic planes from crystals grown with or without nitrogen flow. The structural and optical investigation showed that the central part of the samples exhibited a very good crystalline quality. The best samples proved to be the {100} growth sectors where the only defects found were stacking faults with a defect density under 103 cm-1. At the edges, i.e. between two adjacent growth sectors, structural investigation by transmission electron microscopy revealed stacking faults and hexagonal polytype inclusions. The nitrogen doping was found not to have an influence on the crystalline quality.
Optically Detected Temperature Dependences of Carrier Lifetime and Diffusion Coefficient in 4H- and 3C-SiC
Authors: ul Hassan Jawad , Ščajev Patrik , Jarašiūnas Kęstutis , Bergman Peder
Published: March 2011

Free carrier dynamics has been studied in 4H- and 3C-SiC in a wide temperature range using time-resolved photoluminescence, free carrier absorption, and light induced transient grating techniques. Considerably high carrier lifetime was observed in 3C-SiC epitaxial layers grown on 4H-SiC substrates using hot-wall CVD with respect to previously reported values for 3C-SiC grown either on Si or on 6H-SiC substrates. The temperature dependences of carrier lifetime and diffusion coefficient for 4H- and 3C-SiC were compared. Shorter photoluminescence decay time with respect to free carrier absorption decay time was observed in the same 4H-SiC sample, while these techniques revealed similar trends in the carrier lifetime temperature dependencies. However, the latter dependences for hot-wall CVD-grown 3C layers were found different if measured by time resolved photoluminescence and free carrier absorption techniques.
Complete Determination of the Local Stress Field in Epitaxial Thin Films Using Single Microstructure
Authors: Camarda Massimo , Anzalone Ruggero , Severino Andrea , Piluso Nicolò , La Magna Antonino , La Via Francesco
Published: March 2011

In this article, using finite element simulations and analytical approaches, we demonstrate that planar rotators[1] can be effectively used to determine both the uniform and gradient residual stresses in thin films with higher accuracy compared to other microstructures.
Raman Study of Bulk Mobility in 3C-SiC Heteroepitaxy
Authors: Piluso Nicolò , Severino Andrea , Camarda Massimo , Canino Andrea , La Magna Antonino , La Via Francesco
Published: March 2011

Micro-Raman spectroscopy has been used to study the dependence between the carrier concentration and electrical mobility in n-doped 3C-SiC films grown on (111) and (100) Si oriented substrates. Local stacking variations observed on the (111) 3C-SiC surface lead to a worse crystal morphology compared to (100) 3C-SiC films resulting in a decrease of the average bulk mobility.
Defects in SiC: Theory
Authors: Gali Adam
Published: March 2011

A brief overview about the recent progress in developing the methods to calculate the properties of defects in solids is given and some recent examples on vacancy-related defects in SiC are presented.
Enhanced Annealing of MeV Ion Implantation Damage in N-Type 4H Silicon Carbide by Thermal Oxidation
Authors: Løvlie Lars S. , Svensson Bengt Gunnar
Published: March 2011

Annealing of the Z1/2 and EH6/7 has been studied by DLTS after ion implantation of MeV Si ions and subsequent annealing in either N2 or O2 at 1150 °C, in the dose range 1 - 4 × 108 Si / cm2. It is found that the annealing rate of these prominent defects is greatly enhanced after thermal oxidation, and in particular close to the surface area, due to injection of a defect species which annihilates with both Z1/2 and EH6/7. The migration part of the diffusion coefficient of the injected defect is established to be in the range 1 – 2 × 10-8 cm2/s, and the measured concentration versus depth profiles of both Z1/2 and EH6/7 are accurately simulated by a simple model.
Polytype Stability of 4H-SiC Seed Crystal on Solution Growth
Authors: Alexander Alexander , Seki Kazuaki , Kozawa Shigeta , Yamamoto Yuji , Ujihara Toru , Takeda Yoshikazu
Published: March 2011

We investigated the polytype transition process from 4H-SiC to 6H-SiC during solution growth from the viewpoint of growth mode. The polarity dependence of the dominant grown polytype was similar to those of the sublimation growth and the CVD growth that 4H-SiC relatively grew stably on the C-face. Moreover, the polytype transition occurred during spiral growth. The 6H-SiC expanded to periphery overgrowing on the 4H-SiC. In contrast, there is no sign that 4H-SiC grew on 6H-SiC.
Influence of Post-Growth Annealing on the Defects Nature and Distribution in VLS Grown (111) 3C-SiC Layers
Authors: Marinova Maya , Andreadou Ariadne , Sun Jian Wu , Lorenzzi Jean , Mantzari Alkyoni , Zoulis Georgios , Jegenyes Nikoletta , Juillaguet Sandrine , Soulière Véronique , Ferro Gabriel , Camassel Jean , Polychroniadis Efstathios K.
Published: March 2011

The current communication focuses on the influence of a post-growth annealing on the evolution of defects inside (111) 3C-SiC layers grown by the Vapour Liquid Solid (VLS) mechanism in SiGe melts on Si-face on- and off axis 6H-SiC substrates. The layers are studied by Transmission Electron Microscopy (TEM) and Low Temperature Photoluminescence (LTPL). It was found that the growth on off-axis substrates results in a 3C-SiC layer containing mainly stacking faults (SFs) and microtwins (MT). The density of MT lamellae and SFs reduces in the layers grown on the on-axis substrate compared to off-axis substrate. In the layers grown on off-axis substrates the annealing strongly reduces the density of SFs inclined to the 3C/6H-SiC interface. Additionally, 3C to 6H polytypic transformation appears only at the interface, most probably starting from substrate step edges. This was only seen on off-axis seed since the step edges are more.
Donor-Acceptor Pair Luminescence of P-Al and N-Al Pairs in 3C-SiC and the Ionization Energy of the P Donor
Authors: Ivanov Ivan G. , Henry Anne , Yan Fei , Choyke Wolfgang J. , Janzén Erik
Published: March 2011

The analysis of the donor-acceptor pair luminescence of P-Al and N-Al pairs obtained recently for the cubic 3C polytype of SiC is viewed in some detail. A detailed consideration is given to the fitting procedure applied to the P-Al and N-Al spectra. Fit with theoretical models of spectra of type I and type II are applied to both N-Al and P-Al experimental spectra, and it is demonstrated that only contribution from P on Si site is observable in the presented samples. The accuracy of the obtained phosphorus ionization energy of 48.1 meV is also discussed.
Observation of Bistable Defects in 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: March 2011

DLTS measurements show bistable behavior of the previously reported EH5 peak in low- and high-energy electron irradiation 4H-SiC. Both reconfiguration processes (A ! B and B ! A) take place above 700 ±C. By isothermal annealing, the reconfiguration rates were determined and the reconfiguration energy was calculated to EA = 2.4±0.2 eV. Since the defect is present already after low-energy electron irradiation, which mainly affects the C atom in SiC, the EH5 peak may be related to defects associated with C-vacancies or C-interstitials
Propagation of Stacking Faults in 3C-SiC
Authors: Nagasawa Hiroyuki , Kawahara Takamitsu , Yagi Kuniaki , Hatta Naoki
Published: March 2011

To quantitatively evaluate the efficacy of stacking fault (SF) reduction methods, Monte Carlo simulations are carried out to reveal the SF distribution on a 3C–SiC (001) surface. SF density decreases with increasing epitaxial layer thickness and reducing size of the substrates. Additionally, SF density depends on interactions between adjoining SFs: annihilation of counter SF-pairs or termination of orthogonal SF-pairs. However, the SF is not entirely eliminated when growth occurs on undulant-Si or switchback epitaxy due to “spontaneous SF collimation”. The simulation shows that effective SF reduction methods, those that enhance the SF termination or annihilation, can theoretically attain the SF density on 3C–SiC (001) below 100 cm-1.
Dislocation Revelation in Highly Doped N-Type 4H-SiC by Molten KOH Etching with Na2O2 Additive
Authors: Yao Yong Zhao , Ishikawa Yukari , Sugawara Yoshihiro , Saitoh Hiroaki , Danno Katsunori , Suzuki Hiroshi , Kawai Yoichiro , Shibata Noriyoshi
Published: March 2011

We have proposed a new wet etching recipe using molten KOH and Na2O2 as the etchant (“KN etching”) for dislocation revelation in highly doped n-type 4H-SiC (n+-4H-SiC). Threading screw dislocations (TSDs) and threading edge dislocations (TEDs) have been clearly revealed as hexagonal etch pits differing in pit sizes, and basal plane dislocations (BPDs) as seashell-shaped pits. This new etching recipe has provided a solution to the problem that conventional KOH etching is not effective for dislocation identification in 4H-SiC if the electron concentration is high (>mid-1018 cm-3). We have investigated the effect of SiC off-cut angle on KN etching and it has been shown that the “KN etching” is applicable for the n+-SiC substrate with off-angle from 0o to 8o.
Impact of Carrier Lifetimes on Non-Destructive Mapping of Dislocations in 4H-SiC Epilayers
Authors: Feng Gan , Suda Jun , Kimoto Tsunenobu
Published: March 2011

Dislocations in 4H-SiC epilayers were imaged nondestructively by means of micro photoluminescence (-PL) mapping at room temperature. The one-to-one correspondence between the individual dislocations and the -PL mapping contrast has been consistently obtained. By analyzing the reduction of the intensity in the -PL mapping image performed at 390 nm (near band-edge emission), we were able to distinguish threading screw dislocations and threading edge dislocations. Furthermore, the contrast of dislocations in PL-intensity mapping image greatly depends on the carrier lifetimes of the 4H-SiC epilayers. Lifetimes longer than 0.5 s are essential to obtain a discernible contrast for the individual dislocations.
Correlation between Thermal Stress and Formation of Interfacial Dislocations during 4H-SiC Epitaxy and Thermal Annealing
Authors: Zhang Xuan , Nagano Masahiro , Tsuchida Hidekazu
Published: March 2011

Interfacial dislocations are frequently observed to form during 4H-SiC epitaxy and thermal annealing. This report attempts to establish the correlation between the distribution of interfacial dislocations and the thermal stress induced by a radial temperature gradient. In addition, it is argued that they are misfit dislocations formed by the interaction between thermal strain and misfit strain.
Investigation of Photoluminescence Emission of Basal Plane Frank-Type Defects in 4H-SiC Epilayers
Authors: Kamata Isaho , Zhang Xuan , Tsuchida Hidekazu
Published: March 2011

Frank-type defects on the basal plane in thick 4H-SiC epitaxial layers converted from threading screw dislocation (TSD) have been characterized by photoluminescence (PL) spectroscopy and PL imaging microscopy. PL emission from the stacking fault (SF) and the Frank partial of the defect was obtained at ~457 nm and >700 nm at room temperature, respectively. The PL emission peaks of two other kinds of Frank-type defects were obtained, and a correspondence between the optical properties and the microscopic structures of the three kinds of defects was clarified.
Effect of Inter-Well Coupling between 3C and 6H in-Grown Stacking Faults in 4H-SiC Epitaxial Layers
Authors: Robert Teddy , Marinova Maya , Juillaguet Sandrine , Henry Anne , Polychroniadis Efstathios K. , Camassel Jean
Published: March 2011

Both 3C and 6H stacking faults have been observed in a low doped 4H-SiC epitaxial layer grown in a hot-wall CVD reactor on a heavily doped (off-axis) 4H-SiC substrate. They appear differently on the different parts of sample, with energetic dispersion ranging from 3.01 eV to 2.52 eV. Since they behave as natural type-II quantum wells in the 4H-SiC matrix, the thickness dependence of the excitonic recombination is investigated using the standard effective mass approximation. The results are discussed in terms of built-in electric field and inter-well coupling effects.
Understanding the Inversion-Layer Properties of the 4H-SiC/SiO2 Interface
Authors: Matocha Kevin , Tilak Vinayak
Published: March 2011

The performance of 4H-SiC power MOSFETs is limited by the less than ideal electron inversion-layer mobility due to the poor quality of the SiC-SiO2 interface. This poor interface causes several undesirable behaviors of the electrical performance of SiC MOSFETs, including: (1) strong shifts in the threshold voltage with temperature, (2) low channel mobility and (3) strong sensitivity of the mobility to the channel doping concentration. These features are explained by a high density of interface states, the high surface electric field induced in SiC inversion layers, and the combined effectsa combination of Coulomb and surface roughness scattering.
Investigation of Surface and Interface Morphology of Thermally Grown SiO2 Dielectrics on 4H-SiC(0001) Substrates
Authors: Hosoi Takuji , Konzono Kohei , Uenishi Yusuke , Mitani Shuhei , Nakano Yuki , Nakamura Takashi , Shimura Takayoshi , Watanabe Heiji
Published: March 2011

Surface and interface morphology of thermal oxides grown on 4-off (0001) oriented 4H-SiC substrates by dry O2 oxidation was investigated using atomic force microscopy (AFM) and transmission electron microscopy (TEM). When step bunching was present on a starting wafer, oxide surface roughness was much larger than that of the starting 4H-SiC surface. This is attributed to the difference in oxidation rate between the terrace and the step face. A step-terrace structure on 4H-SiC(0001) was mostly preserved on the oxide surface, but pronounced oxidation occurred around the step bunching. Cross-sectional TEM observation showed that the SiO2/4H-SiC interface became smoother than the initial surface and the thickness of the SiO2 layer fluctuated. Such SiO2 thickness fluctuation may cause a local electric field concentration when a voltage was applied to the oxide, thus degrading the dielectric breakdown characteristics of 4H-SiC metal-oxide-semiconductor (MOS) devices.
Evaluation of 4H-SiC Carbon Face Gate Oxide Reliability
Authors: Fronheiser Jody , Chatterjee Aveek , Grossner Ulrike , Matocha Kevin , Tilak Vinayak , Yu Liang Chun
Published: March 2011

The gate oxide reliability and channel mobility of carbon face (000-1) 4H Silicon Carbide (SiC) MOSFETs are investigated. Several gate oxidation processes including dry oxygen, pyrogenic steam, and nitrided oxides were investigated utilizing MOS capacitors for time dependent dielectric breakdown (TDDB), dielectric field strength, and MOSFETs for inversion layer mobility measurements. The results show the C-face can achieve reliability similar to the Si-face, however this is highly dependent on the gate oxide process. The reliability is inversely related to the field effect mobility where other research groups report that pyrogenic steam yields the highest electron mobility while this work shows it has weakest oxide in terms of dielectric strength and shortest time to failure.
On the “Step Bunching” Phenomena Observed on Etched and Homoepitaxially Grown 4H Silicon Carbide
Authors: Camarda Massimo , Severino Andrea , Fiorenza Patrick , Raineri Vito , Scalese S. , Bongiorno Corrado , La Magna Antonino , La Via Francesco , Mauceri Marco , Crippa Danilo
Published: March 2011

Using several types of surface analysis (Optical profilometers (OP), Atomic Force Microscopies (AFM), Scanning Electron Microscopies (SEM) and cross-sectional high-resolution Transmission Electron Microscopies (TEM)) we analyze the surface morphologies of misoriented 4H silicon carbide after pre-growth hydrogen etching and homo-epitaxial growths. We observed the characteristic self-ordering of nano-facets on any analyzed surface. This nano-faceting, which should not be confused with step bunching, can be considered as a close-to-equilibrium instability, for this reason can be hindered.
Oxygen Ion Induced Charge in SiC MOS Capacitors Irradiated with Gamma-Rays
Authors: Ohshima Takeshi , Iwamoto Naoya , Onoda Shinobu , Makino Takahiro , Nozaki Shinji , Kojima Kazutoshi
Published: March 2011

Charge induced in 6H-SiC nMOS capacitors by 15 MeV oxygen ion microbeams was measured using Transient Ion Beam Induced Current (TIBIC) before and after gamma-ray irradiations. The peak amplitude of TIBIC signals decreases and the fall time increases with increasing number of incident ions. The decrease in the TIBIC peak eventually saturated. The TIBIC signal can be refreshed to its original shape by applying a positive bias of + 1V to gate oxide. Small decrease in both the peak amplitude of TIBIC signal and collected charge was observed due to gamma-ray irradiation.
Electrically Detected ESR Study of Interface Defects in 4H-SiC Metal-Oxide-Semiconductor Field Effect Transistor
Authors: Umeda T. , Esaki K. , Kosugi Ryouji , Fukuda Kenji , Morishita Norio , Ohshima Takeshi , Isoya Junichi
Published: March 2011

We present an electrically detected electron-spin-resonance (ESR) study on SiO2-SiC interface regions of n-channel lateral 4H-SiC MOSFETs with hydrogen annealing. This characterization technique can reveal electrically active defects that interact with channel currents of the MOSFETs. The defects were observed at 20 K, and were labeled “PH0” and “PH1”, one of which (PH1) exhibited a 1H hyperfine splitting of 5.3 mT.
Emission Phenomenon Observation of Thermal Oxides Grown on N-Type 4H-SiC (0001) Wafer
Authors: Senzaki Junji , Shimozato Atsushi , Koshikawa Kazushige , Tanaka Yasunori , Fukuda Kenji , Okumura Hajime
Published: March 2011

Photo emission phenomenon and reliability of thermal oxides grown on n-type 4H-SiC (0001) wafer have been investigated using photo emission microscope. Thermal oxides were grown by dry oxidation, and treated in nitrous oxide atmosphere as followed by hydrogen post oxidation annealing. An initial photo emission phenomenon with weak intensity exists just after stress current is applied to the thermal oxide. It is confirmed that most initial emission occurred at the same position as dielectric breakdown of the thermal oxide. Also, the initial emission phenomenon was observed in the MOS capacitors broken by extrinsic defects such as threading screw dislocations and surface defects. In addition, the photo emission due to Fowler-Nordheim tunnel current through the thermal oxide has peak intensity at 2.48 eV.
Effect of Increased Oxide Hole Trap Density due to Nitrogen Incorporation at the SiO2/SiC Interface on F-N Current Degradation
Authors: Strenger Christian , Bauer Anton J. , Ryssel Heiner
Published: March 2011

Metal-oxide-semiconductor (MOS) capacitors were formed on 4H-silicon carbide (SiC) using thermally grown silicon dioxide (SiO2) as gate dielectrics, both with and without nitrogen incorporation within the oxide. The field dependence of the charge trapping properties of these structures was analyzed and linked to the observed Fowler-Nordheim current degradation. Furthermore, first considerations were presented that indicate an electron impact emission induced generation of positive oxide trapped charge.
Energy Band Structure of SiO2/4H-SiC Interfaces and its Modulation Induced by Intrinsic and Extrinsic Interface Charge Transfer
Authors: Watanabe Heiji , Kirino Takashi , Kagei Yusuke , Harries James , Yoshigoe Akitaka , Teraoka Yuden , Mitani Shuhei , Nakano Yuki , Nakamura Takashi , Hosoi Takuji , Shimura Takayoshi
Published: March 2011

The energy band structure of SiO2/4H-SiC fabricated on (0001) Si- and (000-1) C-face substrates was investigated by means of synchrotron radiation x-ray photoelectron spectroscopy (SR-XPS). The band structure was found to be dependent on substrate orientation and oxide thickness due to both intrinsic and extrinsic effects that cause charge transfer at the SiO2/SiC interface. Our SR-XPS analysis revealed that the intrinsic conduction band offset of the SiO2/SiC for the C-face substrate is smaller than that for the Si-face. This means that, whereas C-face substrates exhibit high carrier mobility, a problem that is crucial to gate oxide reliability remains for SiC-based metal-oxide-semiconductor (MOS) devices owing to increased leakage current.
Simulation of the Incomplete Ionization of the n-Type Dopant Phosphorus in 4H-SiC, Including Screening by Free Carriers
Authors: Scaburri Raffaele , Desalvo Agostino , Nipoti Roberta
Published: March 2011

The simulation of the incomplete ionization of substitutional dopants in Silicon Carbide (SiC) is often performed using Boltzmann statistics and ionization energy values that do not depend on free carrier concentrations. But in the case of heavy doping Fermi-Dirac statistics is needed, while the case of an inhomogeneous dopants distribution or that of an excess carrier injection requires local free carrier concentration-dependent impurity ionization energies. Here a model for describing partial ionization from diluted to high homogeneous doping densities in SiC and in thermal equilibrium is presented and compared with results on Phosphorus doped 4H-SiC.
Effects of Process Variations on Silicon Carbide Devices for Extreme Environments
Authors: Habib Hassan , Wright Nicolas G. , Horsfall Alton B.
Published: March 2011

The variation in device process parameters is a core issue in the realisation of complex SiC logic for extreme environments. Factorial design was used to study the effect of variation in four key process parameters on the threshold voltage of an n-channel lateral JFET. Each parameter is simultaneously varied by +/-10% from the default value and the individual and combined effects were calculated at 300, 600 and 1000K. Consequently, we show how these variations in device parameters degrade the threshold voltage, VI, and, hence, the noise margin of logic inverter.
Two-Dimensional Modeling of Aluminum-Ion Implantation into 4H-SiC
Authors: Mochizuki Kazuhiro , Yokoyama Natsuki
Published: March 2011

A two-dimensional model of aluminum-ion implantation into 4H-SiC at moderate doses (1011 to 1013 cm-2) has been developed. The model is based on a Monte-Carlo simulation using a binary-collision approximation. This simulation reveals that iso-concentration contours are independent of the orientation of the masking edge. Lateral range straggling is extracted by expressing the lateral-concentration profiles as a one-dimensional dual-Pearson-distribution function multiplied by a Gauss-distribution function. Compared to vertical straggling, the lateral straggling is found to be more weakly dependent on projected range.
Influence of Annealing Parameters on Surface Roughness, Mobility and Contact Resistance of Aluminium Implanted 4H SiC
Authors: Schmitt H. , Haeublein Volker , Bauer Anton J. , Frey Lothar
Published: March 2011

The impact of implantation temperature and dose as well as the annealing process with and without a graphite capping layer on surface roughness, carrier mobility and specific contact resistance are investigated and compared. The use of the capping layer is proven to be particularly advantageous: (1) a deterioration of surface roughness can be avoided even for high dose implantations and (2) the specific contact resistance is reduced. Furthermore, it is shown that a capping layer prevents surface contamination during annealing.
2D Simulation of under-Mask Penetration in 4H-SiC Implanted with Al+ Ions
Authors: Lulli Giorgio , Nipoti Roberta
Published: March 2011

In this work under-mask penetration of Al+ ions implanted in 4H-SiC is investigated by computer simulation based on the Monte-Carlo binary collision approximation (MC–BCA). Results indicate that a small fraction of ions, implanted normal to a (0001) 4H-SiC wafer (8° off-axis towards the {11-20}), is scattered and become channeled in the <1120> directions perpendicular to the <0001> axis. Due to this phenomenon, doped regions with concentration ≤ 10− 4 of the peak value, may extend laterally for a few µm below the edge of a SiO2 mask.
Theoretical Studies for Si and C Emission into SiC Layer during Oxidation
Authors: Hijikata Yasuto , Yaguchi Hiroyuki , Yoshida Sadafumi
Published: March 2011

To understand the structure of SiC–oxide interface more in detail, we propose a profiling theory of Si and C emission into SiC layer during oxidation. Simulations of the depth profiles of Si and C interstitials results in the structures analogous with those observed from a spectroscopic ellipsometry. To determine the diffusivities of Si and C interstitials, we performed capacitance–voltage measurements for examining the re-distribution profiles of nitrogen after oxidation and compared between observed and calculated profile. The calculated nitrogen profiles showed good fits to the observed ones in the case of self-diffusivity of C interstitials magnified by several 10 times for literature value. Finally, we discuss the validity of the proposed theory.
3C-SiC MOS Based Devices: From Material Growth to Device Characterization
Authors: Lorenzzi Jean , Esteve Romain , Jegenyes Nikoletta , Reshanov Sergey A. , Schöner Adolf , Ferro Gabriel
Published: March 2011

In this work we report on the growth and preparation of 3C-SiC(111) material for metal-oxide-semiconductor (MOS) application. In order to achieve reasonable material quality to prepare MOS capacitors several and crucial steps are needed: 1) heteroepitaxial growth of high quality 3C-SiC(111) layer by vapour-liquid-solid mechanism on 6H-SiC(0001) substrate, 2) surface polishing, 3) homoepitaxial re-growth by chemical vapour deposition and 4) use of an advanced oxidation process combining plasma enhanced chemical vapour deposition (PECVD) SiO2 and short post-oxidation steps in wet oxygen. Combining all these processes the interface traps density (Dit)can be drastically decreased down to 1.2  1010 eV-1cm-2 at 0.63 eV below the conduction band. To our knowledge, these values are the best ever reported for SiC material in general and 3C-SiC in particular.
Formation of Periodic Steps on 6H-SiC (0001) Surface by Annealing in a High Vacuum
Authors: Lebedev Sergey P. , Petrov V.N. , Kotousova I.S. , Lavrent’ev A.A. , Dement’ev P.A. , Lebedev Alexander A. , Titkov Alexander N.
Published: March 2011

Influence of high-vacuum annealing at temperatures in the range 1300-1400°C and residual pressure of ~10-6 Torr on the surface of 6H-SiC (0001) wafers has been studied. Auger spectroscopy and RHEED data show that the annealing conditions do not lead to any surface reconstruction of the wafers. Atomic force microscopy reveals atomically flat surface terraces separated by steps of unit-cell height (h = 1.5 nm).
Effect of the Seed Polarity for High Quality 4H-SiC Crystal Grown on 6H-SiC Seed by PVT Method
Authors: Yeo Im Gyu , Lee Tae Woo , Park Jong Hwi , Yang Woo Sung , Ryu Heui Bum , Park Mi Seon , Kim Il Soo , Shin Byoung Chul , Lee Won Jae , Eun Tai Hee , Lee Seung Seok , Chun Myong Chuel
Published: March 2011

The single crystal ingots by using a sublimation technique were grown on 6H-SiC dual-seed crystals with opposite face polarities and then SiC crystal wafers sliced from the SiC ingot were systematically investigated to find out the polarity dependence of the crystal quality. The growth rate of the SiC crystal grown in this study was about 0.2mm/hr. N-type 2’’ SiC crystals exhibiting the 4H- and 6H-SiC polytype were successfully fabricated on C-face and Si-face, respectively. The incorporation of nitrogen donors in the SiC crystals grown on the C-face seed crystal was exhibited to be higher than in SiC crystals grown on a Si-face crystal. When the SiC crystal ingot proceeded to grow, the SiC crystal region grown on the C-face seed crystal was enlarged compared to the SiC crystal region on the Si-face seed crystal.
Characterization of Al-Based High-k Stacked Dielectric Layers Deposited on 4H-SiC by Atomic Layer Deposition
Authors: Usman Muhammad , Pilvi T. , Leskelä Markku , Schöner Adolf , Hallén Anders
Published: March 2011

Aluminum-based high-k dielectric materials have been studied for their potential use as passivation for SiC devices. Metal-insulator-semiconductor structures were prepared and their dielectric properties were analyzed using capacitance-voltage and current-voltage measurements. Atomic layer deposition was used for the deposition of dielectric layers consisting of AlN with or without a buffer layer of SiO2, and also a stack of alternating AlN and Al2O3 layers. It has been observed that AlN has a polycrystalline structure which provides leakage paths for the current through the grain boundaries. However, adding alternate amorphous layers of Al2O3 prevent this leakage and give better overall dielectric properties. It is also concluded that the breakdown of the dielectric starts from the degradation of the thin interfacial SiO2 layer.
Improved Characteristics of SiC MOSFETs by Post-Oxidation Annealing in Ar at High Temperature
Authors: Kato Muneharu , Nanen Yuichiro , Suda Jun , Kimoto Tsunenobu
Published: March 2011

Post-oxidation annealing (POA) in Ar at high temperature has been performed during fabrication of 4H-SiC metal-oxide-semiconductor field-effect transistors (MOSFETs). The gate oxides were formed by thermal oxidation followed by N2O annealing, then annealed in Ar for 30 min or 5 h at 1300 °C. The results of Secondary Ion Mass Spectrometry (SIMS) measurements indicated that the C atoms accumulated at the SiO2/SiC interface by thermal oxidation diffused during the 5h-Ar annealing. The characteristics of n-channel MOSFETs were improved and the peak value of field effect mobility was increased to 33 cm2/Vs from 19 cm2/Vs by extending the Ar annealing time.
Improvement of Schottky Contact Characteristics by Anodic Oxidation of 4H-SiC
Authors: Kimura Masaya , Kato Masashi , Ichimura Masaya
Published: March 2011

Anodic oxidation was performed to 4H-SiC in order to suppress the negative impacts on the Schottky diode characteristics. The electrochemical deposition of ZnO before and after the oxidation revealed a reduction in the number of areas with low Schottky barrier height. Before and after the oxidation, current-voltage characteristics of Ni Schottky contacts was compared, and it was found out that the characteristics were improved after the oxidation. These results suggest that the anodic oxidation is a promising technique to suppress the negative influence of the crystal defects.
Investigation of Epitaxial SiC PiN Diodes with Variable Mesa Height
Authors: Pâques Gontran , Scharnholz Sigo , Konrath Jens Peter , Dheilly Nicolas , Planson Dominique , De Doncker Rik W.
Published: March 2011

With the aim of investigating the specific process parameters of bipolar semiconductor devices, simple mesa-terminated silicon carbide PiN diodes were designed and fabricated. The expected effect of the mesa height on the reverse behaviour could be investigated as well as the condition of the material surface. It was shown that these simple devices are well suited as test devices.
Control of Inclined Sidewall Angles of 4H-SiC Mesa and Trench Structures
Authors: Koketsu Hidenori , Hatayama Tomoaki , Amishima Kento , Yano Hiroshi , Fuyuki Takashi
Published: March 2011

The sloped sidewall angle in 4H-SiC mesa structure could be controlled by a thermal etching at 900oC in chlorine (Cl2) based ambience. 4H-SiC C face with 8o off substrate was used. The SiO2 layers for the etching mask were formed by a deposited SiO2 layer or a thermally oxidized layer. Thermal etching was carried out at Cl2 ambience at 900oC for 15 minutes. The surface morphologies of the mesa structures were observed with the scanning electron microscope (SEM) and atomic force microscope (AFM). The sloped angles at the mesa sidewalls using deposited SiO2 mask and thermal SiO2 mask were about 23o and 60o, respectively. These results mean that the angle of sloped sidewall can change by mask fabrication method.
β-SiC NWs Grown on Patterned and MEMS Silicon Substrates
Authors: Watts Bernard Enrico , Attolini Giovanni , Rossi Francesca , Bosi Matteo , Salviati Giancarlo , Mancarella Fulvio , Ferri Matteo , Roncaglia Alberto , Poggi Antonella
Published: March 2011

Cubic silicon carbide nanowires (-SiC or 3C-SiC NW) have been grown by Vapour Phase Epitaxy on (001) silicon substrates patterned by conventional photolithography and on Micro Electro Mechanical Systems (MEMS, e.g. cantilevers, springs, bridges) fabricated on (001) Silicon On Insulator (SOI) wafers. The NW morphology was investigated by scanning electron microscopy, showing that the nanowires grew selectively where a nickel thin layer was previously deposited, thanks to its catalytic action. High resolution transmission electron microscopy studies showed that the NWs are predominantly 3C polytype with <111> growth axis and stacking defects on (111) planes.
Influence of Oxygen on the Absorption of Silicon Carbide Nanoparticles
Authors: Vörös Marton , Deák Peter , Frauenheim Thomas , Gali Adam
Published: March 2011

We have investigated the absorption of 0.9, 1.4 nm silicon carbide nanoparticles (SiC NPs) by time-dependent density functional calculations, focusing on the effect of different oxygen adsorbates of the surface. We have found that negatively charged Si-O−, Si-COO− defects dramatically lower the optical gap of SiC NPs. Our findings can help interpret recent controversary experiments on colloidal SiC NPs.
Advances in Silicon Carbide Single Photon Detectors
Authors: Vert Alexey V. , Soloviev Stanislav I. , Sandvik Peter M.
Published: March 2011

We present overview of achieved results on 4H-SiC avalanche photodiodes (APDs) and arrays. Cost-effective solar-blind optical filter allows achieving high solar photon rejection ratio of more than 106 in combination with more than 40% single photon detection efficiency at 266nm. Three iterations of devices were fabricated and evaluated to compare their optical and electrical properties. Dark count rates and single photon detection efficiencies are the main characteristics compared for these three iterations of device designs.