bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of 4H–SiC DMOSFETs for High–Power Electronics Applications
Authors: Green Ronald , Ogunniyi Aderinto , Ibitayo Dimeji , Koebke Gail , Morgenstern Mark , Lelis Aivars J. , Dickens Corey , Hull Brett A.
Published: March 2009

In this paper, large area (0.18cm2) SiC DMOSFETs with 1.2 kV and 20 A rating are
evaluated for power electronic switching applications. A drain-to-source voltage drop VDS of 2 V at a
forward drain current of 20 A (JD = 110 A/cm2) was obtained and a specific on-resistance of 18
mΩ-cm2 was extracted at room temperature. The device on-resistance was measured up to 150°C and
initially decreases with increasing temperature, but remains relatively flat over the entire temperature
range, demonstrating stable device behavior. High voltage blocking of 1.2 kV between 25°C and
150°C is also demonstrated with a gate-to-source voltage VGS = 0 V. The drain leakage current under
reverse bias and high temperature stress is shown to increase from 10 μA at 25°C to 27 μA at 150°C
while maintaining the full blocking rating of the device. Experimental results from double-pulse
clamped inductive load tests are presented demonstrating fast high voltage and high current switching
capability. High voltage resistive-switching measurements on parallel connected SiC DMOSFETs
were performed with VDS having rise and fall times of 49 and 74 ns respectively. Thermal camera
images taken of parallel connected DMOSFET die during repetitive switching operation with VDS =
420 V, IDS = 25 A and a 40% duty cycle shows a 2°C difference in die temperature, which suggests
even current sharing and temperature stable device operation.
A 13 kV 4H-SiC n-Channel IGBT with Low Rdiff,on and Fast Switching
Authors: Das Mrinal K. , Zhang Q. Jon , Callanan Robert , Capell Craig , Clayton Jack , Donofrio Matthew , Haney Sarah K. , Husna Fatima , Jonas Charlotte , Richmond Jim , Sumakeris Joseph J.
Published: March 2009

For the first time, high power 4H-SiC n-IGBTs have been demonstrated with 13 kV
blocking and a low Rdiff,on of 22 mWcm2 which surpasses the 4H-SiC material limit for unipolar
devices. Normally-off operation and >10 kV blocking is maintained up to 200oC base plate
temperature. The on-state resistance has a slight positive temperature coefficient which makes the
n-IGBT attractive for parallel configurations. MOS characterization reveals a low net positive fixed
charge density in the oxide and a low interface trap density near the conduction band which produces
a 3 V threshold and a peak channel mobility of 18 cm2/Vs in the lateral MOSFET test structure.
Finally, encouraging device yields of 64% in the on-state and 27% in the blocking indicate that the
4H-SiC n-IGBT may eventually become a viable power device technology.
SiC Based Optically-Gated High-Power Solid-State Switch for Pulsed-Power Application
Authors: Mazumder Sudip K. , Sarkar Tirthajyoti
Published: March 2009

Hybrid SiC pulsed-power switch (having bipolar transistor structure) with 5 kV breakdown voltage
and 1 kA peak current rating has been designed, which can be triggered optically using a GaAs or SiC
front-end triggering structure with a rise time < 20 ns and for sub-microsecond pulse-widths. Structural details
and physics-based simulation results are presented. It is shown, that GaAs triggering structure reduces the
optical-triggering power requirement significantly without sacrificing switching speed as compared to a SiC
optical-triggering structure.
Avalanche Multiplication and Impact Ionisation in Separate Absorption and Multiplication 4H-SiC Avalanche Photodiodes
Authors: Loh W.S. , David John P.R. , Soloviev Stanislav I. , Cha H.Y. , Sandvik Peter M. , Ng J.S. , Johnson C. Mark
Published: March 2009

The hole dominated avalanche multiplication characteristics of 4H-SiC Separate
Absorption and Multiplication avalanche photodiodes (SAM-APDs) were determined experimentally
and modeled using a local multiplication model. The 0.5x 0.5mm2 diodes had very low dark current
and exhibited sharp, uniform breakdown at about 580V. The data agree with modeling result using
extrapolated impact ionization coefficients reported by Ng et al. and is probably valid for electric
fields as low as ~0.9MV/cm at room temperature provided that both the C-V measurements and
electric field determination in this work are correct. The packaged devices demonstrate a positive
temperature coefficient of breakdown voltage for temperatures ranging from 100K to 300K which is a
desired feature for extreme environment applications.
Schottky Barrier Lowering in 4H-SiC Schottky UV Detector
Authors: Sciuto Antonella , Roccaforte Fabrizio , Di Franco Salvatore , Raineri Vito
Published: March 2009

The Schottky barrier lowering in 4H-SiC interdigit Schottky-type UV photodiode is investigated in
the presence of a thermally grown oxide layer on the exposed active area. Gain photocurrent is
observed and correlated with the presence of the oxide and with the charge traps at the
semiconductor/oxide interface. Photo-thermally stimulated current measurements evidenced that
interface charge accumulation is optically promoted. Rise and fall photo-current measurements
provided the time parameter of the trapping phenomenon.
SiC-4H Epitaxial Layer Growth by Trichlorosilane (TCS) as Silicon Precursor at Very High Growth Rate
Authors: La Via Francesco , Izzo Gaetano , Mauceri Marco , Pistone Giuseppe , Condorelli Giuseppe , Perdicaro L.M.S. , Abbondanza Giuseppe , Portuese F. , Galvagno G. , Di Franco Salvatore , Calcagno Lucia , Foti Gaetano , Valente Gian Luca , Crippa Danilo
Published: March 2009

The growth rate of 4H-SiC epi layers has been increased up to 100 µm/h with the use of trichlorosilane instead of silane as silicon precursor. The epitaxial layers grown with this process have been characterized by electrical, optical and structural characterization methods. Schottky diodes, manufactured on the epitaxial layer grown with trichlorosilane at 1600 °C, have higher yield and lower defect density in comparison to diodes realized on epilayers grown with the standard epitaxial process.
Status of GaN-Based Power Switching Devices
Authors: Hikita Masahiro , Ueno Hiroaki , Matsuo Hisayoshi , Ueda Tetsuzo , Uemoto Yasuhiro , Inoue Kaoru , Tanaka Tsuyoshi , Ueda Daisuke
Published: March 2009

State-of-the-art technologies of GaN-based power switching transistors are reviewed, in
which normally-off operation and heat spreading as technical issues. We demonstrate a new operation
principle of GaN-based normally-off transistor called Gate Injection Transistor (GIT). The GIT
utilizes hole-injection from p-AlGaN to AlGaN/GaN hetero-junction which increases electron
density in the depleted channel resulting in dramatic increase of the drain current owing to
conductivity modulation. The fabricated GIT on Si substrate exhibits the threshold voltage of +1.0V
with high maximum drain current of 200mA/mm. The obtained on-state resistance (Ron·A) and
off-state breakdown voltage (BVds) are 2.6mΩ·cm2 and 800V, respectively. These values are the best
ones ever reported for GaN-based normally-off transistors. In addition, we propose the use of
poly-AlN as surface passivation. The AlN has at least 200 times higher thermal conductivity than
conventional SiN so that it can effectively reduce the channel temperature.
Progress in GaN MOSFET Technology
Authors: Chow T. Paul , Huang W. , Khan T. , Matocha K. , Wang Y.
Published: March 2009

GaN MOS capacitors were characterized to optimize the electric properties of SiO2/GaN
interface. With optimized anneal conditions, an interface state density of 3.8×1010/cm2-eV was
estimated at 0.19 eV near the conduction band and decreases deeper into the band gap.
Enhancement-mode GaN MOSFETs were experimentally demonstrated on both p and n GaN epilayer
with record high field-effect mobility of 167 cm2/V-s. Lateral RESURF-type GaN MOSFETs exhibit
non-destructive high voltage (up to 940V) blocking capabilities. Other characterization including
mobility orientation dependence, MOS-gated Hall mobility, current collapse and an NMOS inverter
utilizing E/D mode GaN MOSFETs have also been experimentally demonstrated.
Characterization of Traps in GaN pn Junctions Grown by MOCVD on GaN Substrate Using Deep-Level Transient Spectroscopy
Authors: Tokuda Yutaka , Matsuoka Youichi , Ueda Hiroyuki , Ishiguro Osamu , Soejima Narumasa , Kachi Tetsu
Published: March 2009

Minority- and majority-carrier traps were studied in GaN pn junctions grown
homoepitaxially by MOCVD on n+ GaN substrates. Two majority-carrier traps (MA1,MA2) and
three minority-carrier traps (MI1, MI2, MI3) were detected by deep-level transient spectroscopy.
MA1 and MA2 are electron traps commonly observed in n GaN on n+ GaN and sapphire substrates.
No dislocation-related traps were observed in n GaN on n+ GaN. Among five traps in GaN pn on
GaN, MI3 is the main trap with the concentration of 2.5x1015 cm-3.
Characterization of V-Defects in InGaN Single-Quantum-Well Films at Nanometer Level by High Spatial Resolution Cathodoluminescence Spectroscopy
Authors: Yoshikawa Masanobu , Murakami Masataka , Fujita Takaya , Inoue K. , Matsuda K. , Ishida H. , Harima Hiroshi
Published: March 2009

We have measured cathodoluminescence (CL) spectra in the vicinity of V-defects in InGaN
single-quantum-well(SQW) films at nanometer level, using newly developed CL apparatus
(SE-SEM-CL). From spectroscopic CL measurement, it has been found that the spectra change
dramatically in the vicinity of V-defects in the region of £50nm. The SE-SEM-CL has a potential to
detect the CL spectral variation at spatial resolution with £50nm.
Correlation between Screw Dislocations Distribution and Cathodoluminescence Spectra of InGaN Single Quantum Well Films
Authors: Fujita Takaya , Mitani Takeshi , Murakami Masataka , Yoshikawa Masanobu , Harima Hiroshi
Published: March 2009

We have studied InGaN single-quantum-well (SQW) films using atomic force microscopy
(AFM) and cathodoluminescence (CL) spectroscopy. It has been found that a screw dislocations
(SDs) distribution in the height image by AFM is well correlated with images of the CL spectra at
about 440nm assigned to the spontaneous emission from the InGaN SQW. These results at least
mean an existence of non-radiative recombination centers within the InGaN SQW films. It has been
also found that the average period of the peak-intensity and the FWHM change is smaller than that of
the peak-wavelength change assigned to InN mole fluctuations. These results suggest that the exciton
diffusion length of the spontaneous emission at about 440nm is not larger than the average period of
InN mole fluctuations in the InGaN SQW.
288 V-10 V DC- DC Converter Application Using AlGaN/GaN HFETs
Authors: Yoshida Seikoh , Masuda Mitsuru , Niiyama Yuki , Li Jiang , Ikeda Nariaki , Nomura Takehiko
Published: March 2009

We report on the 288 V-10 V DC- DC converter circuit using AlGaN/GaN HFETs for
the first time. The AlGaN/GaN HFET with a large current and a high breakdown voltage operation
was fabricated. That is, the maximum drain current was over 50 A, and the minimum on-resistance
was 70 mohm. The breakdown voltage was over 600 V. A DC-DC down-converter from input DC
288 V to output DC 10 V was fabricated using these HFETs. It was confirmed that the switching
speed of the AlGaN/GaN HFET was faster than that of Si MOSFET. The DC-DC down-converter
was fabricated using these HFETs. This converter was composed of a full bridge circuit using four
n-channel AlGaN/GaN HFETs. In the case of AlGaN/GaN HFET, a gate switching wave (Vgs) and
source-drain wave (Vds) were abrupt compared with those of using Si MOSFETs. In both cases, a
stable and constant output DC 10V was also obtained and the conversion efficiency of the
converters with AlGaN/GaN HFETs was 84%.
Multiple Ion-Implanted GaN/AlGaN/GaN HEMTs with Remarkably Low Parasitic Source Resistance
Authors: Nomoto Kazuki , Satoh Masataka , Nakamura Tohru
Published: March 2009

It is demonstrated that Si ion implantation is useful to fabricate GaN/AlGaN/GaN HEMTs
with extremely low gate leakage current and low source resistance without any recess etching process.
The source/drain regions were formed using Si ion implantation into undoped GaN/AlGaN/GaN on
sapphire substrate. Using ion implantation into source/drain regions with energies of 30 and 80 keV,
the performances were significantly improved. On-resistance reduced from 9.9 to 3.5 Ω·mm.
Saturation drain current and maximum transconductance increased from 300 to 560 mA/mm and
from 75 to 160 mS/mm, respectively.
The Effect of Ohmic Contact Location on the Buffer Leakage Current of AlGaN/GaN Heterostructure
Authors: Choi Young Hwan , Lim Ji Yong , Cho Kyu Heon , Ji In Hwan , Han Min Koo
Published: March 2009

The effect of ohmic contact location on the buffer leakage current of AlGaN/GaN
heterostructure was investigated and the AlGaN/GaN HEMT employing the proposed ohmic
contact pattern was fabricated. We have fabricated 3 different types of ohmic patterns; type A - both
contacts are on the etched GaN buffer layer, type B - one is on the etched GaN buffer layer and the
other is on the unetched GaN cap layer and type C - both contacts are on the unetched GaN cap
layer. Our experimental results showed that the ohmic contact on GaN buffer increased the buffer
leakage current due to the lateral diffusion of ohmic metals. The proposed AlGaN/GaN HEMT
successfully decreased the leakage current and did not affect the forward drain current and the
transconductance.
Investigation of Triangular Defects in 4H-SiC 4° Off Cut (0001) Si Face Epilayers Grown by CVD
Authors: Shrivastava Amitesh , Muzykov Peter G. , Pearman B. , Angel S. Michael , Sudarshan Tangali S.
Published: March 2009

Triangular defects and inverted pyramid type defects formed during homoepitaxial growth on 4H-SiC Si face, 4° off-cut towards [11-20] direction have been investigated. Growth parameters responsible for triangular defect formation were identified and optimized for its reduction in this study. It was found that although the high temperature reduces the density of inverted pyramid type defects, it is not the only remedy for reducing their density and cleanliness of susceptor along with the initial growth condition plays a major role in the formation of these defects.
Influence of Substrate Preparation and Epitaxial Growth Parameters on the Dislocation Densities in 4H-SiC Epitaxial Layers
Authors: Kallinger Birgit , Thomas Bernd , Friedrich Jochen
Published: March 2009

Basal Plane Dislocations (BPD) in SiC are thought to cause degradation of bipolar devices as they can trigger the formation and expansion of stacking faults during device operation. Therefore, epilayers without any BPD are strongly recommended for the achievement of long-term reliable bipolar devices. Such epilayers can be achieved by supporting the conversion of BPD into Threading Dislocations (TD), which depends on the epitaxial growth mode (as described in literature). In this work, the influence of several pre-treatments of the SiC substrate prior to epitaxial growth and different epitaxial growth parameters on the reduction of the BPDs in the SiC epilayers was investigated on 4° off-axis substrates. The dislocation content in substrates and epilayers was determined by Defect Selective Etching (DSE) in molten KOH. The averaged BPD density in epitaxial layers can be reduced to < 100 cm-2 for substrate preparation techniques and to < 30 cm-2 for well-suited epitaxial growth parameters. A certain combination of epitaxial growth parameters leads to < 3 BPD/cm2 in the epitaxial layer.
Solution Growth of Off-Axis 4H-SiC for Power Device Application
Authors: Hattori Ryo , Kusunoki Kazuhiko , Yashiro Nobuyuki , Kamei Kazuhito
Published: March 2009

Solution growth on off-axis 4H-SiC sublimation substrate as a buffer layer for the subsequent CVD epitaxial growth was investigated. Dislocation conversion and propagation from the substrate to the CVD epitaxial layer through the solution grown buffer layer was inspected by molten KOH etch pit observation. Effective dislocation conversion from BPD to TED as an effect of the buffer layer insertion with no drastic change in the total EPD was confirmed.
Strain in 3C–SiC Heteroepitaxial Layers Grown on (100) and (111) Oriented Silicon Substrates
Authors: Zielinski Marcin , Portail Marc , Chassagne Thierry , Cordier Yvon
Published: March 2009

We discuss the influence of the growth conditions (composition of the gaseous phase, growth duration, growth temperature) and wafer properties (orientation, miscut, thickness) on the residual strain of 3C-SiC films grown on silicon substrates. We show that the strain related effects are observed for both studied orientations however some of them (namely the creep effects) were up to now stated only for (100) oriented layers. We also point out the main difference in strain control between the (111) and (100) orientations.
Growth on Rhombohedral (01-1n) Plane: An Alternative for Preparation of High Quality Bulk SiC Crystals
Authors: Filip Octavian , Epelbaum Boris M. , Li Juan , Bickermann Matthias , Xu Xian Gang , Winnacker Albrecht
Published: March 2009

Results on bulk growth of SiC crystals along rhombohedral [01-1n] directions are presented. 6H- and 4H-crystals were grown on rhombohedral planes, which make angles of about 45o with the (0001) plane. Etching features on three differently oriented planes cut from characteristic crystals were compared. Utmost care was concentrated on defect development in the case of non-conventional growth orientation using the seed cut from a “standard” (0001) crystal, containing a typical (standard for [0001] growth) set of crystal defects. We clearly distinguished between a transient layer adjacent to the seed and the main crystal body grown at latter stages. The defect selection and/or transformation in the transient layer appeared strongly depending on the SiC polytype and growth direction. This study brings directly the information on stability of particular defects in the chosen crystal orientation and allows us to distinguish between defects characteristic for [0001] and rhombohedral growth.
Heteroepitaxial Growth of 3C-SiC on Si (111) Substrate Using AlN as a Buffer Layer
Authors: Zhao Yong Mei , Sun Guo Sheng , Liu Xing Fang , Li Jia Ye , Zhao Wan Shun , Wang L. , Li Jin Min , Zeng Yi Ping
Published: March 2009

Using AlN as a buffer layer, 3C-SiC film has been grown on Si substrate by low pressure chemical vapor deposition (LPCVD). Firstly growth of AlN thin films on Si substrates under varied V/III ratios at 1100oC was investigated and the (002) preferred orientational growth with good crystallinity was obtained at the V/III ratio of 10000. Annealing at 1300oC indicated the surface morphology and crystallinity stability of AlN film. Secondly the 3C-SiC film was grown on Si substrate with AlN buffer layer. Compared to that without AlN buffer layer, the crystal quality of the 3C-SiC film was improved on the AlN/Si substrate, characterized by X-ray diffraction (XRD) and Raman measurements.
Aspects of Dislocation Behavior in SiC
Authors: Dudley Michael , Chen Yi , Huang Xian Rong , Ma Rong Hui
Published: March 2009

A review is presented of the current understanding of the dislocation configurations
observed in PVT-grown 4H- and 6H-SiC boules and CVD-grown 4H-SiC homoepitaxial layers. In
both PVT-grown boules and CVD-grown epilayers, dislocation configurations are classified
according to whether they are growth dislocations, i.e., formed during growth via the replication of
dislocations which thread the moving crystal growth front, or result from deformation processes
(under either mechanical or electrical stress) immediately following growth, during post growth
cooling, i.e., behind the crystal growth front or during device operation. Possible formation
mechanisms of growth defects in the PVT grown boules, such as axial screw dislocations and
threading edge dislocation walls are proposed. Similarly, possible origins of growth defect
configurations in CVD-grown epilayers, such as Frank faults bounded by Frank partials, BPDs and
TEDs, are also discussed. In a similar way, the origins of BPD configurations resulting from
relaxation of thermal stresses during post-growth cooling of the PVT boules are discussed. Finally,
the susceptibility of BPD configurations replicated into CVD grown epilayers from the substrate
towards Recombination Enhanced Dislocation Glide (REDG) is discussed.
Sense Determination of c-Axis Screw Dislocations in 4H-SiC
Authors: Chen Yi , Huang Xian Rong , Dhanaraj Govindhan , Dudley Michael , Sanchez Edward , MacMillan Mike F.
Published: March 2009

Grazing-incidence synchrotron topography studies of micropipes (MPs) and closed-core
threading screw dislocations (TSDs) have been carried out and the results compared with ray-tracing
simulations. Simulations indicate that both MPs and TSDs appear as roughly elliptically shaped white
features which are canted to one side or the other of the g-vector depending on the dislocation sense
and which have asymmetric perimeters of dark contrast which are greatly enhanced on the side
towards which the feature is canted (again depending on the dislocation sense). For MPs,
observations are generally consistent with this although the cant of the features is more obviously
discerned than the asymmetry in the perimeter contrast. Sense assignment for MPs has been validated
using back-reflection reticulography. For TSDs, observation are again generally consistent with the
simulations although the smaller feature size and the variability in the line direction of the TSDs make
the asymmetry of perimeter contrast a more obvious and reliable way to determine the dislocation
sense than the sense of cant. TSD dislocation senses so obtained were validated using back-reflection
images of same-sign and opposite-sign pairs.
Growth of Crack-Free 100mm-Diameter 4H-SiC Crystals with Low Micropipe Densities
Authors: Nakabayashi Masashi , Fujimoto Tatsuo , Katsuno Masakazu , Ohtani Noboru , Tsuge Hiroshi , Yashiro Hirokatsu , Aigo Takashi , Hoshino Taizo , Hirano Hosei , Tatsumi Kohei
Published: March 2009

The theromoelastic stress in post-growth SiC crystals has been investigated in order to suppress the cracks which were frequently observed in SiC crystals with larger diameters. Optimizing the temperature distribution in growing crystals lead to reduction of tensile stress components, and thus resulting in crack-free 100mm diameter SiC crystals with micropipe (MP) densities of 0.025/cm2. The concept of process optimization we established is confirmed to be effective to the growth of large diameter SiC crystals with mechanical stability.
Application of 6H to 4H Polytype Conversion to Effective Reduction of Micropipes in 4H SiC Crystals
Authors: Grasza Krzysztof , Tymicki Emil
Published: March 2009

Bulk crystals of 6H and 4H silicon carbide have been grown by PVT method. 6H-SiC were obtained in optimized near-to-equilibrium growth conditions in order to improve the crystal quality and to provide the 6H seeds for 6H to 4H-SiC conversion. In experiments of 6H to 4H polytype transformation a set of invariable growth conditions was applied: C-face seed, C-rich atmosphere, on-axis seed orientation, pre-heating of the source material, slightly convex crystallization front and optimized geometry of the growth system. Other growth parameters were varied to optimize the polytype conversion, e.g.: structural quality of the seed, intentionally added impurity (N and/or Sc), initial growth stage recipe, argon pressure and temperature gradient - resulting in variety of growth rates and temperatures of the seed. Special attention was paid to seed passivation and a scheme of temperature and inert gas pressure changes during growth. Crystals were characterized by KOH etching, X-ray diffraction, optical and AFM microscopy. A reproducible method of 75% efficient conversion was elaborated. A large central surface free of micropipes was observed with characteristic six symmetrical ridges as well as the increased concentration of nitrogen. The parasitic 15R-SiC polytype was nucleated on the vicinal part of the crystallization front of 6H-SiC and 4H-SiC crystals.
Contrast of Basal Plane and Threading Edge Dislocations in 4H-SiC by X-Ray Topography in Grazing Incidence Geometry
Authors: Matsuhata Hirofumi , Yamaguchi Hirotaka , Nagai Ichiro , Ohno Toshiyuki , Kosugi Ryouji , Kinoshita Akimasa
Published: March 2009

Dislocations in a substrate wafer of 4H-SiC with an epi-layer were observed using
technique of monochromatic synchrotron X-ray topography in a grazing incidence geometry. Six
different Burgers vectors of basal plane dislocations and threading edge dislocations were identified
by changing the Bragg reflections, and by analysis of images of dislocation. We identify some
relations of the Burgers vector and the dislocation contrast observed for g=11 2 8. Some of these
relationships are discussed in this report.
Slip of Basal Plane Dislocations in 4H-SiC Epitaxy
Authors: Ohno Toshiyuki
Published: March 2009

Slip of basal plane dislocations in 4H-SiC epitaxy is observed by synchrotron reflection
X-ray topography. It is verified that average slip distance and slip thickness increase with
decreasing donor concentration of epilayer. Since N atom, which is incorporated at carbon site in
4H-SiC and acts as a donor, has a smaller radius than that of C atom, lattice contraction effect is
expected due to incorporation of N. Considering difference of lattice contraction between the
substrate and the epilayer owing to difference of donor concentration, strain in the epilayer is
estimated. The strain is expected to increase with decreasing the donor concentration of epilayer
and the results are explained from this point of view.
Raman Scattering Study of Stress Distribution around Dislocation in SiC
Authors: Matsuoka D. , Yamamoto H. , Nishino Shigehiro , Hasuike Noriyuki , Kisoda Kenji , Harima Hiroshi
Published: March 2009

We have presented a combined method of microscopic measurements between Raman
scattering and polarizing optical microscope to characterize inhomogeneous residual stress
distributions around dislocations in 4H- and 6H-SiC wafers. First, stressed portions were found in
wafers by an optical polarizing microscope under a crossed Nicole arrangement. Then, the portions
were examined by Raman-imaging technique for lateral variations of phonon spectra. The residual
stresses were quantified from the phonon-peak frequency shift using a known frequency-shift rate for
6H-SiC. Characterization to the depth direction was also conducted by surface etching with molten
KOH. The stresses typically amounted to the order of 100 MPa. In a 4H-SiC homoepitaxial wafer
sample, we observed threading dislocations transferred from the substrate to the epitaxial layer, and
found that larger stress fields existed in the epitaxial layer than the substrate. We also observed stress
distributions around compressively stressed sub-grain boundaries.
Intrinsic Defects in HPSI 6H-SiC: an EPR Study
Authors: Carlsson Patrick , Son Nguyen Tien , Magnusson Björn , Henry Anne , Janzén Erik
Published: March 2009

High-purity, semi-insulating 6H-SiC substrates grown by high-temperature chemical vapor
deposition were studied by electron paramagnetic resonance (EPR). The carbon vacancy (VC), the
carbon vacancy-antisite pair (VCCSi) and the divacancy (VCVSi) were found to be prominent defects.
The (+|0) level of VC in 6H-SiC is estimated by photoexcitation EPR (photo-EPR) to be at ~ 1.47 eV
above the valence band. The thermal activation energies as determined from the temperature
dependence of the resistivity, Ea~0.6-0.7 eV and ~1.0-1.2 eV, were observed for two sets of samples
and were suggested to be related to acceptor levels of VC, VCCSi and VCVSi. The annealing behavior of
the intrinsic defects and the stability of the SI properties were studied up to 1600°C.
Behavior of Native Defects in Semi-Insulating 4H-SiC after High Temperature Anneals and Different Cool-Down Rates
Authors: Garces N.Y. , Glaser E.R. , Carlos W.E. , Fanton Mark A.
Published: March 2009

We have recently explored the nature and stability of native defects in high-purity
semi-insulating 4H-SiC bulk substrates grown by PVT and HTCVD methods after post-growth
anneal treatments up to 2400oC using electron paramagnetic resonance (EPR) and low-temperature
photoluminescence (PL) experiments. In the present study we have extended these investigations to
SI 4H-SiC subjected to the same post-growth high-temperature anneal treatments, where significantly
enhanced carrier lifetimes have been reported for such conditions, but cooled at different rates ranging
from ~2-25oC/min. Previously, the intensities of the native defects decreased monotonically with
anneals from 1200–1800oC; however, it was recently observed that several of these defects reappear
after annealing at 2100oC and above. Our results illustrate the effects of the post-growth anneal
treatments and cool-down rates on the concentrations of native defects.
Occurrence of Polytype Transformation during Nitrogen Doping of SiC Bulk Wafer
Authors: Chen J. , Lien S.C. , Shin Y.C. , Feng Zhe Chuan , Kuan C.H. , Zhao J.H. , Zhao J.H. , Lu Wei Jie
Published: March 2009

The polytype structural variations of a set of SiC bulk wafers with different Nitrogen (N) doping levels, prepared by Physical Vapore Deposition (PVD), are studied. The initial growth conditions were used to produce 6H-polytype SiC, which has been approved for the undoped and lightly doped materials. However, when extreme high N-dopants were applied, the obtained wafer was found with 4H- and 15R-polytype features. Our experimental results of HR-TEM and Raman scattering have revealed clearly the polytype transformation, indicating that the inducement of N in the reactor leads to the polytype transformation of the resulted SiC crystal.
The Electronic Structure of the UD-4 Defect in 4H, 6H and 15R SiC
Authors: Gällström Andreas , Magnusson Björn , Thuaire Aurelie , PASKOV Plamen , Henry Anne , Janzén Erik
Published: March 2009

The photoluminescence (PL) of the UD-4 defect is observed in semi-insulating bulk 4H,
6H and 15R SiC. In 4H and 6H SiC the UD-4 defect consists of two families of no-phonon (NP) lines,
Ua and Ub, and in 15R SiC it consists of three families, Ua, Ub and U15R. The Ua family in 4H, 6H
and 15R all show similar temperature behavior with higher energy NP lines becomming observable at
higher temperatures. In the case of the Ub and U15R families, a luminescence line with lower energy
than the prominent luminescence line appears at higher temperatures. The polarization and Zeeman
measurements suggest that the defect has C3v symmetry.
New Type of Defects Explored by Theory: Silicon Interstitial Clusters in SiC
Authors: Gali Adam , Hornos T. , Son Nguyen Tien , Janzén Erik
Published: March 2009

We have studied the small clusters of silicon and carbon interstitials by ab initio
supercell calculations in 4H-SiC. We found that silicon interstitials can form stable and electrically
active complexes with each other or with a carbon interstitial. Local vibration modes and
ionization energies were also calculated in order to help the identification of the defects. We
propose that silicon interstitials can emit from these clusters at relatively high temperatures,
which may play an important role in the formation of the DI center.
Effect of the Schottky Barrier Height on the Detection of Midgap Levels in 4H-SiC by Deep Level Transient Spectroscopy
Authors: Reshanov Sergey A. , Pensl Gerhard , Danno Katsunori , Kimoto Tsunenobu , Hishiki Shigeomi , Ohshima Takeshi , Yan Fei , Devaty Robert P. , Choyke Wolfgang J.
Published: March 2009

The effect of the Schottky barrier height on the detection of the midgap defects EH6
and EH7 in 4H-SiC by deep level transient spectroscopy (DLTS) is systematically studied.
The results show that the DLTS peak height - and as a consequence the observed defect
concentration - increases with the increasing barrier height and saturates above 1.5 eV for EH6
and above 1.7 eV for EH7, while below 1.1 eV the DLTS peak height completely disappears.
A model is applied, which determines the position of the quasi-Fermi level in the space
charge region as a function of the barrier height and of the reverse bias applied and which
explains the variation of the DLTS peak height.
Evolution of D1-Defect Center in 4H-SiC during High Temperature Annealing
Authors: Maximenko Serguei I. , Freitas Jaime A. , Garces N.Y. , Glaser E.R. , Fanton Mark A.
Published: March 2009

The behavior of the D1 center in semi-insulating 4H-SiC substrates revealed by
low-temperature photoluminescence was investigated after post-growth high temperature anneals
between 1400 and 2400oC. The influence of different post-anneal cooling rates was also studied. The
optical signature of D1 was observed up to 2400oC with intensity maxima at 1700 and 2200oC. We
propose that the peak at 1700°C can be related to the formation and subsequent dissociation of SiC
native defects. It was found that changes in the post-annealing cooling rate drastically influence the
behavior of the D1 center and the concentrations of the VC, VSi, VC-VSi and VC-CSi lattice defects.
Identification of Neutral Carbon Vacancy-Carbon Anti-Site Complex by Low Temperature Photoluminescence Spectroscopy
Authors: Steeds John W.
Published: March 2009

A common set of optical centres found in photoluminescence spectra of electron
irradiated 4H SiC is interpreted as originating in neutral carbon-vacancy carbon anti-site pairs.
Simulation Study for HTCVD of SiC Using First-Principles Calculation and Thermo-Fluid Analysis
Authors: Kito Yasuo , Makino Emi , Inaba Kenji , Hosokawa Norikazu , Hiramatsu Hidehiko , Hasegawa Jun , Onda Shoichi , Tsuboi Hideyuki , Takaba Hiromitsu , Miyamoto Akira
Published: March 2009

A simulation study for high temperature chemical vapor deposition (HTCVD) of silicon carbide (SiC) is presented. Thermodynamic properties of the species were derived from the first-principles calculations in order to evaluate the activation energy (Ea) in the gas phase reaction. Pathways producing SiC2 and Si2C from SiCl4-C3H8-H2 system were proposed to investigate the effect of chlorinated species on HTCVD. A thermo-fluid analysis was carried out to estimate the partial pressures of the species. It was found that the main sublimed species of Si, SiC2, Si2C decreased in the SiCl4-C3H8-H2 system compared to the SiH4-C3H8-H2 system. This suggests that the growth rate would decrease in the atmosphere of chlorinated species at around 2500°C.
Origin of Giant Step Bunching on 4H-SiC (0001) Surfaces
Authors: Ishida Yuuki , Takahashi Tetsuo , Okumura Hajime , Arai Kazuo , Yoshida Sadafumi
Published: March 2009

To elucidate the origin of giant step bunching on 4˚ off-axis 4H-SiC (0001) faces, we
carried out hydrogen etching and epitaxial growth under various conditions. We found that giant step
bunching occurs during hydrogen etching and epitaxial growth at extremely low or high C/Si ratios,
i.e., with an excessive supply of SiH4 or C3H8. From these results, we have proposed that the origins
of giant step bunching are asymmetry in the step kinetics in etching and Si or C cluster generation on
terraces during growth.
SiC Polytype Stability Influenced by Ge Impurities
Authors: Nader Richard , Kazan Michel , Moussaed E. , Zgheib Charbel , Nsouli Bilal , Pezoldt Joerg , Masri Pierre M.
Published: March 2009

In this paper we present a methodology to affect the stability of polytypes formation
during heteroepitaxial growth of SiC on Si. This methodology is based on the investigation of
growth related parameters. These parameters involve substrate temperature, effect of impurities on
surface diffusion, strain, and super-saturation conditions as solved by using SSMBE growth (Solid
Source molecular beam epitaxy).
Dots Formation by CVD in the SiC-Si Hetero-System
Authors: Bechelany Mikhael , Ferro Gabriel , Dazord Jacques , Cornu David , Miele Philippe
Published: March 2009

The formation of dots by CVD in the hetero-system SiC-Si was studied in the two
possible ways : Si dots on SiC substrate and SiC dots on Si substrate. The substrates underwent
special surface treatment to reveal a network of parallel steps before deposition of the dots. In the Si
on SiC case, the dots density on the 8°off 4H-SiC substrate varied in the range 107 – 7x108 cm-2 and
mainly depends on the SiH4 flux and the deposition time. The Si dots are in majority aligned along
the step edges of the substrate. In the other hetero-system, only propane was introduced in the
reactor to performed a localised carbonisation of the Si(111) 1.5°off substrate. The SiC dots
obtained at 1200°C have similar density the Si ones but with smaller size.
Electronic Band Structure of Cubic Silicon Carbide Nanowires
Authors: Miranda A. , Ramos A. Estrella , Cruz Irisson M.
Published: March 2009

In this work, the effects of the diameter and morphology on the electronic band structure of
hydrogenated cubic silicon carbide (b-SiC) nanowires is studied by using a semiempirical sp3s*
tight-binding (TB) approach applied to the supercell model, where the Si- and C-dangling bonds on
the surface are passivated by hydrogen atoms. Moreover, TB results (for the bulk) are compared with
density functional calculations in the local density approximation. The results show that though
surface morphology modifies the band gap, the change is more systematic with the thickness
variation. As expected, hydrogen saturation induces a broadening of the band gap energy because of
the quantum confinement effect.
Dynamical Simulation of SiO2/4H-SiC Interface on C-Face Oxidation Process: From First Principles
Authors: Ohnuma Toshiharu , Miyashita Atsumi , Iwasawa Misako , Yoshikawa Masahito , Tsuchida Hidekazu
Published: March 2009

We perform a dynamical simulation of the SiO2/4H-SiC C-face interface oxidation process
at 2500K using first-principles molecular dynamics based on plane waves, supercells, and the
projector-augmented wave method. The slab model is used for the simulation. Oxygen molecules are
dissociated in the SiO2 layers or by Si atoms at the SiO2 interface. The O atoms of the O2 molecule
oxidize the C atoms at the SiC interface and form Si-C-O or CO2-C complexes. COx (x=1 or 2)
molecules are desorbed from these complexes by thermal motion. COx molecules diffuse in the SiO2
layers when they do not react with dangling bonds. COx molecule formed during C-face oxidation
more easily diffuse than those formed during Si-face oxidation in the interface region.
Laser Doping of Chromium and Selenium in p-Type 4H-SiC
Authors: Bet S. , Quick N.R. , Kar Aravinda
Published: March 2009

Chromium (Cr) and selenium (Se) are laser doped in silicon carbide (4H-SiC p-type
aluminium) to fabricate an embedded light emitting device and to tune the light emission. A near
infrared Nd:YAG (1064 nm wavelength) laser source and an organometallic Cr compound (bis
(ethyl benzene)-chromium) and organometallic Se compound (dimethyl selenide) were used to laser
dope SiC. A p-n junction device structure was created using these dopants. The dopant profiles have
been characterized using secondary ion mass spectrometry. Electrical properties were measured
using Hall effect measurement. Enhanced diffusivity and solubility with complete activation of
dopants was observed for laser doped Cr and Se. Cr and Se are unconventional dopants, which
serve as a double donor and a double acceptor respectively, while aluminium (Al) behaves as single
acceptor and nitrogen (N) as a single donor in SiC. The defect levels (donor and acceptor) created
within the forbidden band gap of SiC due to Se, Cr and Al onsets the donor acceptor pair (DAP)
recombination mechanism for luminescence observed in SiC. Electroluminescence studies showed
an orange (677 nm) corresponding to Cr-Al and, red (698 nm) and white (380-900 nm) for Se-Al
and pure white for Cr-Se-Al. The Cr-Se-Al white light exhibited a correlated color temperature of
4935 K, which compares well to average daylight (5500 K).
Electrical Characteristics of Ti/4H-SiC Slicidation Schottky Barrier Diode
Authors: Kinoshita Akimasa , Nishi Takashi , Ohyanagi Takasumi , Yatsuo Tsutomu , Fukuda Kenji , Okumura Hajime , Arai Kazuo
Published: March 2009

The reaction and phase formation of the Ti/SiC Schottky contact as a function of the
annealing temperature (400~700oC) were investigated. The Schottky barrier height (fb) and the
crystal structure of the samples annealed at the different temperature were measured by the forward
current-voltage (IV) characteristics and the x-ray diffraction (XRD), respectively. XRD
measurements were performed in the w-2q scan and the pole figure measurement for Ti (101)
diffraction peak. The fb was changed as a function of temperature. It was concluded that the fb
variation and non-uniformity of the samples annealed at 400oC, 500oC, 600 oC and 700oC was caused
by changing the condition at the interface between SiC substrate and Ti. We fabricated the 600V
Ti/SiC silicidation SBD annealed at 500oC for 5min. As a result, a low forward voltage drop, low
reverse leakage current and stability at high temperature (200 oC) for the Ti/SiC silicidation SBD were
shown.
Investigation of Subcontact Layers in SiC after Diffusion Welding
Authors: Korolkov Oleg , Sleptsuk Natalja , Sitnikova Alla A. , Viljus Mart , Rang Toomas
Published: March 2009

In our early analytic reports [1,2] has been made the supposition that during the diffusion
welding (DW) in subcontact area of SiC is formed the intermediate amorphous layer. In the present
work are given the first results of transmission electron microscopy (TEM) and electron diffraction
investigations of subcontact layers in n0-n- 4H-SiC. TEM examinations show that the boundary
between aluminium and silicon carbide looks like stripy interface layer of ~ 25 nm thickness. This
is the evidence that during diffusion welding in subcontact surface layer of SiC the shear micro
deformations have been taking place and due to this process the plane inclusions of small-grained
phase have been appeared. The image of contact area obtained in diffracted SiC rays (dark field)
apparently confirms that stripy zone belongs to silicon carbide because the aluminium (black zone)
fell out of contrast. Diffraction picture obtained from bulk zone of silicon carbide looks like
monocrystallin, but the micro diffraction pattern obtained from the subcontact (stripy zone) gives a
lot of concentric rings, that makes evidential the fact of existence of small-grained inclusions.
Deciphering of this electron-diffraction pattern reveals the presence of such elements as residue
SiC, Al, Si, as well as inclusions of graphite.
Model Calculation of SiC Oxidation Rates in the Thin Oxide Regime
Authors: Hijikata Yasuto , Yamamoto Takeshi , Yaguchi Hiroyuki , Yoshida Sadafumi
Published: March 2009

To explain the growth rate enhancement of SiC oxidation in the thin oxide regime, which
was recently found from the real time monitoring experiments of the initial oxidation stage of SiC
(000–1) C-face using an in-situ spectroscopic ellipsometer, we tried to apply the interfacial Si
emission model, which has been originally proposed for Si oxidation, and found that the Si emission
model successfully reproduced the SiC oxidation rates at the whole range of oxide thickness and at
oxidation temperatures measured. By comparing with the simulations for Si oxidation, we have
discussed the oxidation mechanism of SiC.
Structural Characterization of CF-PVT Grown Bulk 3C-SiC
Authors: Mantzari Alkyoni , Mercier Frédéric , Soueidan Maher , Chaussende Didier , Ferro Gabriel , Polychroniadis Efstathios K.
Published: March 2009

The aim of the present work is to study the structural properties of 3C-SiC which is grown on (0001) 6H-SiC and on (100) 3C-SiC (Hoya) seeds using the Continuous Feed Physical Vapor Transport (CF-PVT) method. Transmission Electron Microscopy (TEM) observations confirm that the overgrown layer is of the 3C-SiC polytype. In the case of the 6H-SiC substrate, microtwins (MTs), stacking faults (SFs) and dislocations (D) are observed at the substrate-overgrown interface with most of the dislocations annihilating within the first few µm from the interface. In the case of 3C-SiC crystals grown on 3C seeds, repeated SFs are formed locally and also coherent (111) twins of 3C-SiC are frequently observed near the surface. The SF density is reduced at the uppermost part of the grown material.
High Frequency Inversion Capacitance Measurements for 6H-SiC n-MOS Capacitors from 450 to 600 °C
Authors: Ghosh Ruby N. , Loloee Reza , Isaacs-Smith Tamara , Williams John R.
Published: March 2009

The operation of metal-oxide-semiconductor (MOS) devices based on the semiconductor SiC in
high temperature environments above 300 °C requires an understanding of the physical processes in
these capacitor structures under operating conditions. In this study we have focused on the regime
of inversion biasing, where the electrical characteristics of the device are dominated by minority
carriers. We report on the direct observation of the high frequency inversion capacitance due to
thermal generation of holes in 6H-SiC n-MOS capacitors between 450 and 600 °C by monitoring
the 1MHz C-V characteristics of large area, 1000 μm diameter, capacitors in the dark. Our
experimental results are consistent with a first order calculation based on the delta depletion
approximation.
Interface and Carrier Transport Behaviour in Al/HfO2/SiO2/SiC Structure
Authors: Mahapatra Rajat , Horsfall Alton B. , Wright Nicolas G.
Published: March 2009

In this study we report interface and carrier transport behaviour in Al/HfO2/SiO2/SiC MIS structure.
The density of the interface states (Dit) and the oxide trapped charges (Not) are found to be ~7 x 1011
eV-1cm-2 @ Ec-Et = 0.2 eV, and ~ 4.8 x 1011 cm-2. The temperature dependencies on gate current
density are explored to study the different charge transport mechanisms through the HfO2-based
dielectric stack on 4H-SiC. In the low voltage region, the conduction mechanism is controlled by a
space charge limited or electronic hopping conduction process. Beyond this region (1.25 MV/cm
<E <2.45MV/cm), leakage current consists of combination of Pool-Frenkel (PF) and Schottky
emission The trap energy level is found to be ~0.6 eV. In the higher field region (> 2.5 MV/cm),
and at higher temperatures Schottky emission (SE) fits the data very well. The barrier height is
found to be ~1.5 eV, which is higher than the value for just HfO2 on SiC
Effect of Gate Wet Reoxidation on Reliability and Channel Mobility of Metal-Oxide-Semiconductor Field-Effect Transistors Fabricated on 4H-SiC(000-1)
Authors: Suzuki Takuma , Senzaki Junji , Hatakeyama Tetsuo , Fukuda Kenji , Shinohe Takashi , Arai Kazuo
Published: March 2009

The channel mobility and oxide reliability of metal-oxide-semiconductor field-effect
transistors (MOSFETs) on 4H-SiC (0001) carbon face were investigated. The gate oxide was
fabricated by using dry-oxidized film followed by pyrogenic reoxidation annealing (ROA).
Significant improvements in the oxide reliability were observed by time-dependent dielectric
breakdown (TDDB) measurement. Furthermore, the field-effect inversion channel mobility (μFE) of
MOSFETs fabricated by using pyrogenic ROA was as high as that of conventional 4H-SiC (0001)
MOSFETs having the pyrogenic-oxidized gate oxide. It is suggested that the pyrogenic ROA of dry
oxide as a method of gate oxide fabrication satisfies both channel mobility and oxide reliability on
4H-SiC (0001) carbon-face MOSFETs.
TDDB Measurement of Gate SiO2 on 4H-SiC Formed by Chemical Vapor Deposition
Authors: Fujihira Keiko , Yoshida Shohei , Miura Naruhisa , Nakao Yukiyasu , Imaizumi Masayuki , Takami Tetsuya , Oomori Tatsuo
Published: March 2009

The reliability of CVD gate oxide was investigated by CCS-TDDB measurement and
compared with thermally grown gate oxide. Although the QBD of thermal oxide becomes smaller for
the larger oxide area, the QBD of CVD oxide is almost independent of the investigated gate oxide
area. The QBD at F = 50% of CVD oxide, 3 C/cm2, is two orders of magnitude larger for the area of
1.96×10-3 cm2 at 1 mA/cm2 compared to that of thermal oxide. More than 80% of the CVD oxide
breakdown occurs at the field oxide edge and more than 70% of the thermal oxide breakdown in the
inner gate area. These results suggest that the lifetime of CVD oxide is hardly influenced by the
quality of SiC, while the defects and/or impurities in SiC affect the lifetime of thermally grown
oxide.