bluuebunny/crossref_metadata_2025 huggingface dataset:
High-Temperature (up to 800 K) Operation of 6-kV 4H-SiC Junction Diodes
Authors: Levinshtein Michael E. , Ivanov Pavel A. , Boltovets Mykola S. , Krivutsa Valentyn A. , Palmour John W. , Das Mrinal K. , Hull Brett A.
Published: March 2009

Steady-state and transient characteristics of packaged 6-kV 4H-SiC junction diodes have
been investigated in the temperature range Т = 300 – 773 К. Analysis of the forward current-voltage
characteristics and reverse current recovery waveforms shows that the lifetimeτ of non-equilibrium
carriers in the base of the diodes steadily increases with temperature across the entire temperature
interval. The rise in τ and decrease in carrier mobilities and diffusion coefficients with increasing
temperature nearly compensate each other as regards their effect on the differential resistance of the
diode, Rd. As a result, Rd is virtually temperature independent. An appreciable modulation of the
base resistance takes place at room temperature even at a relatively small current density j of 20
A/cm2. At T = 800 K and j = 20 A/cm2, a very deep level of the base modulation has been observed.
The bulk reverse current is governed by carrier generation in the space-charge region via a trap with
activation energy of 1.62 eV. The surface leakage current of packaged structures does not exceed
2×10-6 А at T = 773 K and a reverse bias of 300 V.
Improving Switching Characteristics of 4H-SiC Junction Rectifiers Using Epitaxial and Implanted Anodes with Epitaxial Refill
Authors: Losee Peter A. , Li Can Hua , Kumar R.J. , Chow T. Paul , Bhat I. , Gutmann Ronald J. , Stahlbush Robert E.
Published: March 2009

The on-state and switching performance of high voltage 4H-SiC junction rectifiers are
compared using numerical simulations and experimental characterization. Epitaxial and implanted
anode PiN diodes as well as novel, advanced rectifiers have been fabricated in 4H-SiC using 110μm
thick drift layers. The relatively low forward voltage drop of these epi-anode diodes (4.2V @
100A/cm2) indicates moderate conductivity modulation, while the superior switching performance
of the “MPS-like” rectifiers is demonstrated with reverse recovery characteristics at various
temperatures and forward current densities.
Investigation of Packaged High-Voltage 4H SiC pin Diodes in the 20-700 °C Temperature Range
Authors: Boltovets Mykola S. , Basanets Volodymyr V. , Camara Nicolas , Krivutsa Valentyn A. , Zekentes Konstantinos
Published: March 2009

The packaged microwave 4H SiC pin diode chips (with i-region length of 6 μm, mesa
diameter of 80 μm and blocking voltage of 1000 V) were investigated. We studied the parameters
of diode I−V curve (in particular, the diode resistance RS at forward current) and the processes of
diode switching from forward current of 50 mA to reverse voltage of 15 V, as well as C−V curves,
in the 20−700 °C temperature range.
At a voltage of 300 V, the diode reverse current was 10 (180) μA when temperature was
600 (700) °C. At a forward current of 40 mA, the diode resistance first decreases smoothly as
temperature is increased from 20 up to 300 °C, and then grows up. As temperature is increased from
20 up to 700 °C, the effective lifetime τeff grows from 7 up to 50 ns, while the diode capacitance (in
the 0−40 V reverse voltage range) grows smoothly as temperature is increased from 20 up to
400 °C.
Numerical Investigation of SiC Devices Performance Considering the Incomplete Dopant Ionization
Authors: Udal Andres , Velmre Enn
Published: March 2009

The temperature-dependences of ionized dopant concentration at different doping levels
are generalized and the preconditions for thermal instabilities due to self-heating are studied. The
nonisothermal simulations of forward-biased SiC structures over a wide temperature range are
performed by using the drift-diffusion 1D-simulator DYNAMIT. Results show that the incomplete
doping ionization will be an important effect if impurity activation energies exceed 0.1, 0.2 and
0.3 eV for doping levels 1019, 1018 and 1017cm−3, respectively. For appearance of S-shaped selfheated
I/V curves the respective values must exceed 0.2, 0.3 and 0.4 eV. Strong influence of
incomplete dopant ionization on forward I/V curves of realistic 4H-SiC and 6H-SiC p-i-n structures
is predicted by simulations. At that the dominating role of the thick substrate layer is shown.
Optimization of the Specific On-Resistance of 4H-SiC BJTs
Authors: Balachandran S. , Chow T. Paul , Agarwal Anant K.
Published: March 2009

We evaluate the performance capabilities and limitations of high voltage 4H-SiC based
Bipolar Junction Transistors (BJTs). Experimental forward characteristics of a 4kV BJT are studied
and simulations are employed to determine the factors behind the higher than expected specific onresistance
(Ron,sp) for the device. The impact of material (minority carrier lifetimes), processing
(surface recombination velocity) and design (p contact spacing from the emitter mesa) parameters
on the forward active performance of this device are discussed and ways to lower Ron,sp, below the
unipolar level, and increase the gain (β) are examined.
High Temperature Characterization of 4H-SiC Bipolar Junction Transistors
Authors: Krishnaswami Sumi , Agarwal Anant K. , Richmond Jim , Capell Craig , Ryu Sei Hyung , Palmour John W. , Geil Bruce , Katsis Dimos , Scozzie Charles
Published: March 2009

This paper summarizes the recent demonstration of 3200 V, 10 A BJT devices with a
high common emitter current gain of 44 in the linear region, and a specific on-resistance of 8.1 mΩ-
cm2 (10 A at 0.90 V with a base current of 350 mA and an active area of 0.09 cm2). The onresistance
increases to 40 mΩ-cm2 at 350°C, while the DC current gain decreases to 30. A sharp
avalanche behavior was observed with a leakage current of 10 μA at a collector voltage of 3.2 kV.
SiC-Based MOSFETs for Harsh Environment Emissions Sensors
Authors: Sandvik Peter M. , Ali Majdeddin , Tilak Vinayak , Matocha Kevin , Stauden Thomas , Tucker Jesse B. , Deluca John , Ambacher Oliver
Published: March 2009

Depletion-mode 4H-SiC FETs were fabricated for use as harsh environment gas sensors.
To enable sensitivity to NOx, O2 and H2 gases, metal oxide catalysts such as InOx were integrated
into the gate of the device. The FETs had a total area of approximately 1 mm2. Devices with
various gate widths and lengths were fabricated and tested, with sensor performance of 5% or
greater in current change from the baseline resulting from designs having a length to width ratio of
around 50.
Investigation of In-Grown Dislocations in 4H-SiC Epitaxial Layers
Authors: Kojima Kazutoshi , Kato Tomohisa , Kuroda Satoshi , Okumura Hajime , Arai Kazuo
Published: March 2009

We have investigated the generation of new dislocations during the epitaxial growth of
4H-SiC layers. Dislocations were mainly propagated from the substrate into the epitaxial layer.
However, it was found that some amount of new threading edge dislocations (TEDs) and basal plane
dislocations (BPDs) were generated during the epitaxial growth. The generation of those dislocations
appeared to depend on the in-situ H2 etching conditions, not the epitaxial growth conditions. By
optimizing in-situ H2 etching condition, we were able to effectively suppress the generation of new
dislocations during epitaxial growth, and obtain 4H-SiC epitaxial layers which have the equivalent
etch pit density (EPD) to the substrates. Our additional investigation of the conversion of BPDs to
TEDs revealed that its efficiency similarly depends on in-situ H2 etching. We were able to obtain a
high conversion efficiency of 97 % by optimizing the in-situ H2 etching conditions before epitaxial
growth.
Anisotropic Properties of GaN Studied by Raman Scattering
Authors: Lin H.C. , Feng Zhe Chuan , Chen Ming Song , Shen Ze Xiang , Lu Wei Jie , Collins W.E.
Published: March 2009

The phonon anisotropy property of the GaN wurtzite crystal is studied using angular
dependent Raman spectroscopy both theoretically and experimentally. The polarized Raman
scattering spectra were recorded from cross-sections of c-axis oriented GaN films as a function of
the angle between the incident laser polarization direction and the film normal direction in three
different configurations. The Raman intensity of A1(TO) showed a sinusoidal dependence on the
rotating angle, as also did the E1(TO) mode, while the E2 mode has a quite different behavior. The
theoretical fit takes into account the susceptibility contribution and the phase differential of
different vibrating elements.
Structural Characterization of Bulk AlN Single Crystals Grown from Self-Seeding and Seeding by SiC Substrates
Authors: Raghothamachar Balaji , Dalmau Rafael , Dudley Michael , Schlesser Raoul , Zhuang Dejin , Herro Ziad , Sitar Zlatko
Published: March 2009

Using a combination of synchrotron white beam x-ray topography (SWBXT) and high
resolution x-ray diffraction (HRXRD), the structural quality of AlN crystals grown by various
sublimation-based techniques have been non-destructively analyzed. Spontaneously nucleated AlN
crystals are characterized by very low defect densities but their size is small. Self-seeding results in
nucleation of multiple grains of different orientations, a few of which are of good quality while most
are highly strained. Using readily available commercial 4H and 6H-SiC substrates, several growth
runs have been carried out using different growth conditions to obtain thick AlN layers, either
attached to the seed or free-standing. While attached layers are typically cracked and highly strained,
crack-free free-standing layers can be obtained by delamination or SiC decomposition. X-ray
characterization reveals these crystals have good purity but moderately high defect densities.
Growth and Investigation of n-AlGaN/p-6H-SiC/n-6H-SiC Heterostructures
Authors: Lebedev Alexander A. , Ledyaev O. Yu. , Strel'chuk Anatoly M. , Kuznetsov Alexey N. , Cherenkov A.E. , Nikolaev A.E. , Zubrilov A.S. , Seredova Natasha V. , Volkova A.A.
Published: March 2009

The investigated AlGaN epitaxial layers were grown by hydride vapor phase epitaxy
(HVPE) on a commercial P+ SiC substrate or on an N+ SiC Lely substrate with a p+ SiC layer
previously grown by sublimation epitaxy. To investigate the electrical characteristics of the n-p
heterojunction, mesa structures of 100, 200 and 1500 microns in diameter were fabricated by
reactive ion etching. Investigation of electrical characteristics shows good quality of grown n-
AlGaN/p-SiC heterojunctions. This shows applicability of this technological combination for
producing n-AlGaN/p-SiC bipolar or FET transistors.
Optical Characterization of ZnO Materials Grown by Modified Melt Growth Technique
Authors: Feng Zhe Chuan , Yu J.W. , Wang J.B. , Varatharajan R. , Nemeth B. , Nause J. , Ferguson Ian T. , Lu Wei Jie , Collins W.E.
Published: March 2009

ZnO bulk crystal wafers, undoped and doped with various impurities of Ga, Er, Co, Ho,
Fe, Mn, and co-doped Mg-Li, have been prepared by a modified melt growth method, and
characterized by optical techniques of Raman scattering, photoluminescence and UV-visible
transmission. Their wurtzite structures were confirmed, with a small degree of crystalline
imperfection. It is shown that with some dopants, such as, Co and Fe, the electronic energy gap is
affected much less than the optical absorption gap. Computer analysis has helped greatly in obtaining
useful information of the optical properties of the ZnO bulk materials.
Epitaxial Layers Grown with HCl Addition: A Comparison with the Standard Process
Authors: La Via Francesco , Galvagno G. , Firrincieli A. , Roccaforte Fabrizio , Di Franco Salvatore , Ruggiero Alfonso , Barbera Milo , Reitano Ricardo , Musumeci Paolo , Calcagno Lucia , Foti Gaetano , Mauceri Marco , Leone Stefano , Pistone Giuseppe , Portuese F. , Abbondanza Giuseppe , Abagnale Giovanni , Valente Gian Luca , Crippa Danilo
Published: March 2009

The growth rate of 4H-SiC epi layers has been increased by a factor 3 (up to 18μm/h)
with respect to the standard process with the introduction of HCl in the deposition chamber. The
epitaxial layers grown with the addition of HCl have been characterized by electrical, optical and
structural characterization methods. An optimized process without the addition of HCl is reported
for comparison. The Schottky diodes, manufactured on the epitaxial layer grown with the addition
of HCl at 1600 °C, have electrical characteristics comparable with the standard epitaxial process
with the advantage of an epitaxial growth rate three times higher.
Ab Initio Studies of the Surface Reaction of Si2C and SiC2 with Si on the 4H-SiC (000-1) Surface
Authors: Yamaguchi Hiroki , Sakiyama Yukinori , Makino Emi , Onda Shoichi , Matsumoto Yoichiro
Published: March 2009

The origin of the polytypes of SiC has been investigated from the viewpoint of surface
reactions by the density functional theory (DFT) within the Projector Augmented Wave-Generalized
Gradient Approximation. Three radicals were considered here as the major species in the crystal
growth process: Si, Si2C and SiC2. We supposed that these radicals contribute to the crystal growth
directly through the adsorption on the 4H-SiC (000-1) C-face surface. The DFT calculations showed
that the Si2C, which relatively has a similar structure with the SiC crystal, had no activation barrier to
be adsorbed chemically to the 4H-SiC C-face surface. On the other hand, SiC2 with Si showed an
activation barrier of 0.79eV to form the 4H-SiC crystal. In order to investigate the arrangements to
decide polytypism in SiC, we compared the adsorption energies between the different sites, which
correspond to the 4H-SiC crystal and a disordered arrangement. The activation energies had almost no
difference. Our calculations indicated that these radicals do not contribute to the origin of the
polytypes of SiC.
Experimental Observations of Extended Growth of 4H-SiC Webbed Cantilevers
Authors: Trunek Andrew J. , Neudeck Philip G. , Spry David J.
Published: March 2009

We report on further observations of homoepitaxially grown 4H silicon carbide (SiC)
cantilevers on commercial on-axis mesa patterned substrates. Mesa shapes with hollow interiors
were designed to significantly increase the ratio of dislocation-free cantilever area to pregrowth
mesa area. Mesas that did not contain axial screw dislocations (SD’s) continued to expand laterally
until uncontrolled growth in the trench regions rises up to interfere / merge with the laterally
expanding cantilevers. Molten KOH etching revealed high defect density in regions where trench
growth merged with the laterally expanding cantilevers. The remaining portions of the cantilevers,
except for central coalescence points, remained free of dislocations.
6H-SiC Homoepitaxial Growth and Optical Property of Boron- and Nitrogen-Doped Donor-Acceptor Pair (DAP) Emission of 1º-Off Substrate by Closed-Space Sublimation Method
Authors: Kawai Y. , Maeda Tomohiko , Nakamura Yoshihiro , Sakurai Yoji , Iwaya Motoaki , Kamiyama Satoshi , Amano Hiroshi , Akasaki Isamu , Yoshimoto Masahiro , Furusho Tomoaki , Kinoshita Hiroyuki , Shiomi Hiromu
Published: March 2009

We demonstrate high-speed and high-quality 6H-SiC homoepitaxial growth on a
1°-off c-plane SiC substrate by a closed-space sublimation method. By optimizing the size of
single-crystal source materials in the growth system, a high-quality 6H-SiC epilayer with an
X-ray diffraction rocking curve (0006) full-width at the half maximum (FWHM) of 38 arcsec
was obtained. We also carried out doping of nitrogen and boron during the growth of the
SiC epilayer. A strong donor-acceptor pair (DAP) emission at a peak wavelength of 570 nm
under excitation by a 395 nm nitride-based light-emitting diode (LED) was observed. The
6H-SiC with DAP emission is promising for use as a phosphor in a nitride-based LED,
because high-quality nitride layers can be grown on the SiC substrates with small off-oriented
angles.
Improvement of 4H-SiC Selective Epitaxial Growth by VLS Mechanism Using Al and Ge Based Melts
Authors: Ferro Gabriel , Soueidan Maher , Jacquier Christophe , Godignon Philippe , Stauden Thomas , Pezoldt Joerg , Lazar Mihai , Montserrat Josep , Monteil Yves
Published: March 2009

Al-Si and Ge-Si systems were studied for selective epitaxial growth (SEG) of 4H-SiC by
the Vapour-Liquid-Solid mechanism. Al-Si and Ge-Si bilayers stackings were deposited on 8° off,
Si face, 4H-SiC substrates. After patterning of the layers, the samples were heated up to 1000°C and
1220°C, respectively, for Al-Si and Ge-Si stackings in order to melt the layers. Propane was
introduced either during the initial heating ramp, before melting of the alloy, or after reaching the
temperature plateau. It was found that introduction of propane before melting was a key parameter
in order to improve the homogeneity of the deposit. In both cases, SEG of SiC was achieved.
However, the best results were obtained with Ge-Si system giving smooth and uniform ∼100 nm
thick epitaxial deposits on all the pattern sizes and shapes. Ge incorporation in the SiC was found to
be rather limited but homogeneous in the layer.
Enhanced Carrier Lifetime in Bulk-Grown 4H-SiC Substrates
Authors: Jenny Jason R. , Malta D.P. , Tsvetkov V.T. , Das Mrinal K. , McD. Hobgood H. , Carter Jr. Calvin H.
Published: March 2009

To devise a means of circumventing the cost of thick SiC epitaxy to generate drift layers
in PiN diodes for >10kV operation, we have endeavored to enhance the minority carrier lifetimes in
bulk-grown substrates. In this paper, we discuss the results of a process that has been developed to
enhance minority carrier lifetimes to in excess of 30 μs in bulk-grown 4H-SiC substrates.
Measurement of lifetimes was principally conducted using microwave-photoconductive decay
(MPCD). Confirmation of the MPCD lifetime result was obtained by electron beam induced
current (EBIC) measurements. Additionally, deep level transient spectroscopic analysis of samples
subjected to this process suggests that a significant reduction of deep level defects in general and of
Z1/Z2, specifically, may account for the significantly enhanced lifetimes. Finally, a study of
operational performance in devices employing drift layers fabricated from substrates produced by
this process confirmed ambipolar lifetimes in the microsecond range.
Nitrogen-Doping of Polycrystalline 3C-SiC Films Deposited by Low Pressure Chemical Vapor Deposition
Authors: Fu Xiao An , Trevino Jacob , Mehregany Mehran , Zorman Christian A.
Published: March 2009

This paper reports the effect of deposition temperature on the deposition rate, residual
stress, and resistivity of in-situ nitrogen-doped (N-doped) polycrystalline 3C-SiC (poly-SiC) films
deposited by low pressure chemical vapor deposition (LPCVD). N-doped poly-SiC films were
deposited in a high-throughput, resistively-heated, horizontal LPCVD furnace capable of holding up
to 150 mm-diameter substrates using SiH2Cl2 (100%) and C2H2 (5% in H2) precursors, with NH3
(5% in H2) as the doping gas. The deposition rate increased, while the residual stress decreased
significantly as the deposition temperature increased from 825oC to 900°C. The resistivity of the
films decreased significantly from 825°C to 850°C. Above 850°C, although the resistivity still
decreased, the change was much smaller than at lower temperatures. XRD patterns indicated a
polycrystalline (111) 3C-SiC texture for all films deposited in the temperature range studied. SIMS
depth profiles indicated a constant nitrogen atom concentration of 2.6×1020/cm3 in the intentionally
doped films deposited at 900°C. The nitrogen concentration of unintentionally doped films (i.e.,
when NH3 gas flow was zero) deposited at 900°C was on the order of 1017/cm3. The doped films
deposited at 900°C exhibited a resistivity of 0.02 -cm and a tensile residual stress of 59 MPa,
making them very suitable for use as a mechanical material supporting microelectromechanical
systems (MEMS) device development.
Theory of Dislocations in SiC: The Effect of Charge on Kink Migration
Authors: Eberlein T.A.G. , Jones R. , Blumenau A.T.
Published: March 2009

Under forward bias bipolar 4H- and 6H-SiC devices are known to degrade rapidly
through stacking fault formation and expansion in the basal plane. It is believed that the ob-
served rapid stacking fault growth is due to a recombination-enhanced dislocation glide (REDG)
mechanism at the bordering partial dislocations. This degradation phenomenon has generated
considerable interest in the involved dislocations — in particular in their atomic and electronic
structure, but also in the mechanisms of their glide motion. Fortunately, nowadays advances in
computing power and in theoretical methodology allow the ab initio based modelling of some
aspects of the problem. This paper therefore gives a brief review of recent activities in this
field, and further discusses some general problems of ab initio based modelling of dislocations
in compound semiconductors.
Characterization of SiC Crystals by Using Deep UV Excitation Raman Spectroscopy
Authors: Nakashima Shinichi , Mitani Takeshi
Published: March 2009

Raman spectroscopy using deep UV (DUV) light excitation has been applied to
characterizing process-induced defects in surface layers in SiC. Raman spectra of P+-ion implanted
and post annealed SiC have been measured as a function of dose level and annealing temperature. The
recovery of the crystallinity and electrical activity have been evaluated. Precipitation of excess
phosphorus was found in heavily doped specimens. High dose implanted and post annealed samples
show uneven distribution of residual defects, which is demonstrated by mapping of Raman
bandwidth. Damage in 4H-SiC surfaces, which were mechanically polished with various sizes of
abrasives, has been evaluated from DUV micro-Raman measurements. The Raman analysis
demonstrates that bandwidth and peak frequency can be used as monitors of the polish–induced
damage. It is found that localized defects reducing free carrier density remain even after polishing
with small sized abrasives.
Stacking Faults and 3C Quantum Wells in Hexagonal SiC Polytypes
Authors: Miao M.S. , Lambrecht Walter R.L.
Published: March 2009

The electronic driving force for growth of stacking faults (SF) in n-type 4H SiC under
annealing and in operating devices is discussed. This involves two separate aspects: an overall
thermodynamic driving force due to the capture of electrons in interface states and the barriers that
need to be overcome to create dislocation kinks which advance the motion of partial dislocations
and hence expansion of SF. The second problem studied in this paper is whether 3C SiC quantum
wells in 4H SiC can have band gaps lower than 3C SiC. First-principles band structure calculations
show that this is not the case due to the intrinsic screening of the spontaneous polarization fields.
Performance of Silicon Carbide PiN Diodes Fabricated on Basal Plane Dislocation-Free Epilayers
Authors: Zhang Ze Hong , Grekov A.E. , Sadagopan Priyamvada , Maximenko S.I. , Sudarshan Tangali S.
Published: March 2009

The nucleation sites of stacking faults (SFs) during forward current stress operation of
4H-SiC PiN diodes were investigated by the electron beam induced current (EBIC) mode of scanning
electron microscopy (SEM), and the primary SF nucleation sites were found to be basal plane
dislocations (BPDs). Damage created on the diode surface also acts as SF nucleation sites. By using a
novel BPD-free SiC epilayer, and avoiding surface damage, PiN diodes were fabricated which did not
exhibit SF formation under current stressing at 200A/cm2 for 3 hours.
Investigation of Structural Stability in 4H-SiC Structures with Heavy Ion Implanted Interface
Authors: Galeckas Augustinas , Hallén Anders , Schöner Adolf , Linnros Jan , Pirouz P.
Published: March 2009

We investigate the possibility of controlling formation of stacking faults (SFs) at the
interface region by implanting the 4H-SiC substrate with low-energy antimony ions (75 keV Sb+)
prior to conventional CVD growth of the homoepitaxial layers. This approach is based on the solidsolution
hardening concept, according to which interaction of impurity atoms with dislocations
makes the motion of the latter more difficult. Photoluminescence imaging spectroscopy is employed
to investigate incorporation of Sb+ implants at the buried interface and also to assess its impact on
structural degradation. Spectral results are analyzed considering both the onset of n-type doping and
irradiation damage. The latter factor was estimated separately from supplementary measurements of
high-energy (2.5 MeV H+) proton-irradiated 4H-SiC epilayers. We compare results of optically
stimulated SF formation in virgin and Sb implanted regions and provide a comprehensive picture of
the defect evolution, including microscopic details of the imminent nucleation sites.
3-Dimensional Non-Destructive Dislocation Analyses in SiC Measured by Planar Electron-Beam-Induced Current Method
Authors: Yanagisawa Y. , Hatayama Tomoaki , Yano Hiroshi , Uraoka Yukiharu , Fuyuki Takashi
Published: March 2009

Propagations of dislocations in 4H-SiC were evaluated three-dimensionally by a planar
mapping EBIC method with the control of accelerating voltages. Screw dislocation (SD), edge
dislocation (ED), and basal plane dislocation (BPD) were clearly observed through the 20nm-thick
Ni Schottky contact on SiC. From the analysis of BPD extended on {0001}, the intensity of EBIC
signals was proportional to the depth position of defect. In addition, the information of the
decomposition and combination for dislocations can be obtained from the fluctuation of EBIC signal
along the scanning position.
Quenching Photoconductivity and Photoelectric Memory in 6H-SiC
Authors: Duisenbaev M.
Published: March 2009

In this paper superlinear dependence in the intensity–current characteristic, optical and
temperature quenching of photocurrent and photoelectric memory in structures made on the basis of
compensated 6H-SiC at room and high temperatures are reported. The maximal time of decreasing
of the residual current was 5*104 s. With illumination by additional light with 0.62 μm wavelength
and increasing of the applied voltage the value of residual current can be changed. The depth
sensitivity centre is positioned at Ec -1.1eV and the cross section of captured holes on this centre is
10-21-10-22 cm2 based on our measurements.
Thermal Evolution of Defects in Semi-Insulating 4H SiC
Authors: Carlos W.E. , Glaser E.R. , Garces N.Y. , Shanabrook B.V. , Fanton Mark A.
Published: March 2009

High temperature anneals were used to study the evolution of native defects in semiinsulating
(SI), ultrahigh purity SiC using electron paramagnetic resonance (EPR), infrared and
visible photoluminescence (PL) and COREMA (Contactless Resistivity Mapping) measurements.
In EPR we observe a defect that we tentatively identify as VC-CSi-VC. The EPR intensities of this
defect and the UD1 IRPL increase significantly with annealing in all samples.
The Method for Enhancing Nitrogen Doping in 6H-SiC Single Crystals Grown by Sublimation Process: The Effect of Si Addition in SiC Powder Source
Authors: Kim Kwan Mo , Seo Soo Hyung , Kim Jae Woo , Song Joon Suk , Oh Myung Hwan , Bahng Wook , Kim Eun Dong
Published: March 2009

The variation of nitrogen doping concentration was systematically investigated with
respect to the amount of silicon powder added to the SiC powder for growing n-type 6H-SiC single
crystal by the sublimation method. To change intentionally the Si content in the SiC powder, 0wt% to
2wt% of a silicon powder was added to first-thermal treated SiC powder and the mixed powder was
treated again at 1800oC for 3 hours to eliminate excess free-metallic silicon. Nitrogen doped 6H-SiC
single crystals were grown by using 2nd-thermal treatment SiC powder at fixed N2/(Ar + N2) (3%).
The nitrogen doping concentration of 6H-SiC crystals increased with increasing Si content in the SiC
powder. In this work, we could identify that the additional silicon powder in SiC powder plays a role
in the enhancement of nitrogen doping in 6H-SiC crystals grown by the sublimation method.
Trapping Recombination Process and Persistent Photoconductivity in Semi-Insulating 4H SiC
Authors: Kalabukhova Ekaterina N. , Lukin S.N. , Savchenko D.V. , Sitnikov A.A. , Mitchel W.C. , Smith S.R. , Greulich-Weber Siegmund
Published: March 2009

The decay kinetics of a persistent photoconductivity (PPC) in undoped semi-insulating
4H SiC and intercenter charge transfer were studied with EPR, photo-EPR and optical admittance
spectroscopy (OAS). A thermally activated charge transfer process that occurs in the dark has been
observed. The PPC effect was observed directly in changes in the quality factor of the EPR cavity
before and after illumination and by the decay of the OAS signal for deep levels, and indirectly by
the excitation and decay of the nitrogen and boron EPR lines that were not observed in the dark
before illumination. The decay kinetics of the PPC and photo-induced carrier capture by nitrogen
and boron levels were found to follow a stretched exponential form. The PPC in the temperature
range from 77 to 300K was found to be produced by a thermally induced charge transfer process
involving deep trap levels.
Vacancy Defects Induced by Low Energy Electron Irradiation in 6H and 3C-SiC Monocrystals Characterized by Positron Annihilation Spectroscopy and Electron Paramagnetic Resonance
Authors: Kerbiriou X. , Barthe Marie France , Esnouf S. , Desgardin P. , Blondiaux G. , Petite G.
Published: March 2009

In this work we used Positron Annihilation Spectroscopy (PAS) and Electron
Paramagnetic Resonance (EPR) to investigate the properties of vacancy defects produced by low
energy electron irradiation. N-doped 3C-SiC and 6H-SiC monocrystals have been irradiated with
electrons at different energies from 240keV to 900keV. EPR measurements show that Frenkel pairs
VSi
3-/Si are created in 6H-SiC when electron irradiation is performed at low energy (240-360 keV).
EPR also indicates that the silicon displacement threshold energy is higher in 3C-SiC than in 6HSiC.
Moreover, PAS results show that the size and concentration of the vacancy defects decrease
when the electron energy decreases for both polytypes. PAS detects vacancy defects in 240keV
electron irradiated 3C-SiC, and the detection of the carbon vacancy is proposed.
The Optical Admittance Spectroscopy of the Vanadium Donor and Acceptor Levels in Semi-Insulating 4H-SiC and 6H-SiC
Authors: Lee Won Woo , Zvanut Mary Ellen
Published: March 2009

The purpose of this study is to determine the vanadium defect levels in semi-insulating
4H-SiC and 6H-SiC using optical admittance spectroscopy (OAS). OAS data show several distinct
peaks for the vanadium-doped SI 4H-SiC and 6H-SiC. Comparison of the data for the two
polytypes suggests that peaks at 0.67 ± 0.02 eV and 0.70 ± 0.02 eV in 6H substrates and 0.75 ± 0.02
eV in 4H substrates are related to V3+/4+ levels at the cubic sites. A peak at 0.87 ± 0.02 eV in the 6H
sample is assigned to the same defect level at the hexagonal site and the associated transition in 4H
was observed at 0.94 ± 0.02 eV in our spectra. The donor levels are thought to be related to peaks
at 1.94 ± 0.05 eV and 1.87 ± 0.05 eV in 4H and 6H samples, respectively. The differences between
the values obtained from the optical admittance measurements and those reported in the literature
are attributed to thermal relaxation and/or contributions from defect complexes.
Growth and Surface Morphologies of 6H SiC Bulk and Epitaxial Crystals
Authors: Dhanaraj Govindhan , Chen Yi , Dudley Michael , Zhang Hui
Published: March 2009

Bulk crystals and epitaxial layers of 6H SiC have been grown and their surface
morphologies have been investigated. Seeded sublimation has been employed to obtain bulk 6H SiC
crystals whereas a silicon tetrachloride-propane based chemical vapor deposition (CVD) was used
for growing epitaxial layers. The hot-zones were designed using numerical simulation. Growth rates
up to 200 μm/hr could be achieved in the CVD process. A new growth-assisted hydrogen etching was
developed to reveal the distribution of the micropipes present in the substrate. Morphological features
were studied using Nomarski, atomic force microscopy (AFM), and scanning electron microscopy
(SEM), and the structural quality was evaluated using synchrotron X-ray topography.
SiC Pore Surfaces: Surface Studies of 4H-SiC(1-102) and 4H-SiC(-110-2)
Authors: Starke Ulrich , Lee W.Y. , Coletti Camilla , Saddow Stephen E. , Devaty Robert P. , Choyke Wolfgang J.
Published: March 2009

The morphology and atomic structure of 4H-SiC(1102) and 4H-SiC(1102) surfaces, i.e.
the surfaces found in the triangular channels of porous 4H-SiC, have been investigated using AFM,
LEED and AES. After hydrogen etching the surfaces show steps parallel and perpendicular to the caxis,
yet drastically different morphologies for the two isomorphic orientations. Both surfaces
immediately display a sharp LEED pattern. Together with the presence of oxygen in the AES spectra
this indicates the development of an ordered oxide. Both surfaces show an oxygen free, well ordered
surface after Si deposition and annealing.
Characterization of SiC Substrates Using X-Ray Rocking Curve Mapping
Authors: Yoganathan Murugesu , Emorhokpor Ejiro , Kerr Thomas , Gupta A. , Tanner C.D. , Zwieback Ilya
Published: March 2009

SiC substrates produced at II-VI, Inc. have been characterized using x-ray rocking curve
mapping (topography). The rocking curves have been measured in the -scan mode for the (0006)
Bragg reflection of 6H and the (0004) reflection of 4H SiC substrates. The maps contain
information extracted from the rocking curves, such as the peak angle () and the rocking curve
broadening (FWHM). In the case when lattice distortion is present due to the elastic or plastic
deformation, the peak angle () changes gradually upon scanning, with the d/dx gradient
proportional to the lattice curvature in the plane of diffraction. Multi-peak reflections and/or sharp
change in the value of indicate the presence of misoriented grains. X-ray rocking curve mapping
of SiC substrates yields excellent measures of crystalline quality that contain important information
on the lattice strain and sub-grain misorientation.
Columnar Pore Growth in n-Type 6H SiC
Authors: Ke Yue , Yan Fei , Devaty Robert P. , Choyke Wolfgang J.
Published: March 2009

A hybrid columnar and dendritic porous structure has been developed in n-type 6H SiC
using photoelectrochemical etching with proper control of the applied voltage and current density.
The diameter of the formed columnar pores is around 200-500 nm. A possible formation mechanism
due to the spatial distribution of holes and the HF concentration gradient in the pores is proposed. A
self-supporting film with this morphology is a promising candidate for protein dialysis.
Novel Polycrystalline SiC Films Containing Nanoscale Through-Pores by Selective APCVD
Authors: Chen L. , Fu Xiao An , Zorman Christian A. , Mehregany Mehran
Published: March 2009

A selective atmospheric pressure chemical vapor deposition (APCVD) process has been
developed to deposit porous polycrystalline silicon carbide (poly-SiC) thin films containing a high
density of through-pores measuring 50 to 70 nm in diameter. The selective deposition process
involves the formation of poly-SiC films on patterned SiO2/polysilicon thin film multilayers using a
carbonization-based 3C-SiC growth process. This technique capitalizes on significant differences in
the nucleation of poly-SiC on SiO2 and polysilicon surfaces in order to form mechanically-durable,
chemically-stable, and well anchored porous structures, thus offering a simple and potentially more
versatile alternative to direct electrochemical etching.
Sol-Gel Silicon Carbide for Photonic Applications
Authors: Friedel B. , Greulich-Weber Siegmund
Published: March 2009

We have investigated the growth of SiC, following a modified sol-gel process,
which not only allows the realization of 3D photonic bandgap materials but also is useful for
various SiC applications like templates in medicine or filters in harsh environment. Depending
on the sol-gel annealing procedure one obtains macro-porous SiC, amorphous SiC, or
from nano to micrometer-sized 3C-SiC single crystals. At low annealing temperatures preferably
nanowires are grown. Via various sol-gel-annealing procedures we are able to prepare
single crystals with sizes ranging from several nm up to several 100 %m, while the resulting
polytype only depends on the annealing temperature available. Not only for photonic applications
useable procedures for doping with shallow level donors and acceptors as well as with
deep level defects are essential. We show that controlled doping is possible either during the
sol-gel preparation or via the gas phase during the following annealing procedure.
Thermodynamic Analysis of Synthetic Potentialities of the nSiC + SiO2 Starting System: SiC Gas-Phase Transport via Si(g) and CO(g)
Authors: Sevastyanov V.G. , Pavelko R.G. , Ezhov Yu S. , Kuznetsov N.T.
Published: March 2009

The major objective of our studies was the thermodynamic analysis of the nSiС+SiO2
system and revealing potentialities for the implementation of the SiC gas-phase transport
conditions. As a result of thermodynamic scanning of the chemical activity of nSiС+SiO2 system
the conditions for implementing the SiC gas-phase transport were found out within a wide
temperature range. It was found out that the basic process in the gas-phase transport of silicon
carbide is:
SiCs + SiOg→ 2Sig + СОg SiC evaporation at T2
2Sig + СОg → SiCnanowhiskers + SiOg SiC deposition at T1
Sequential evaporation and deposition of silicon carbide result in the growth of SiC crystals
from a gas phase. The processes of SiC gas-phase transport and deposition were experimentally
realized. Synthesized were SiC nanocrystals over 300 μm long, ~ 300 nm in diameter that forms a
three-dimensional subskeleton inside the carbon skeleton.
Correlation between Current Transport and Defects in n+/p 6H-SiC Diodes
Authors: Canino Mariaconcetta , Castaldini Antonio , Cavallini Anna , Moscatelli Francesco , Nipoti Roberta , Poggi Antonella
Published: March 2009

This paper reports on the defects created in a 6H-SiC p-type substrate by a process of ion
implantation and a quite low temperature annealing (1300 °C), suitable for the realization of the
source/drain regions of a MOSFET because it does not give rise to step bunching phenomena.
Current voltage measurements showed the presence of a group of diodes featured by excess current.
The effects of defects under the implanted layer on the transport properties of the diodes were
investigated by DLTS: four hole traps were detected in all the measured diodes; besides, a
broadened peak around 550 K was detected in the diodes that show excess current.
Current Analysis of Ion Implanted p+/n 4H-SiC Junctions: Post-Implantation Annealing in Ar Ambient
Authors: Nipoti Roberta , Bergamini Fabio , Moscatelli Francesco , Poggi Antonella , Canino Mariaconcetta , Bertuccio Giuseppe
Published: March 2009

An n-type 8° off-axis <0001> 4H-SiC epitaxial wafer was processed. The n-type epilayer
had doping and thickness of, respectively, ~3 × 1015 cm-3 and ~5 μm. p+/n diodes with not
terminated junctions were constructed by a selective area implantation process of 9.2 × 1014 cm-2
Al+ ions at 400°C. The diodes had areas in the range 2×10-4
-1×10-3
cm2. The Al depth profile was
6×1019 cm-3 high and 164 nm thick. The post implantation annealing process was done in a high
purity Ar ambient at 1600°C for 30 min. The diode current-voltage characteristics were measured in
the temperature range 25-290°C. Statistics of 50-100 measurements per device type were done.
The fraction of diodes that could be modeled as abrupt junctions within the frame of the Shockley
theory decreased with increasing area value, but was always > 75%. The ideality factor was > 2
only at temperatures > 200°C and bias values < 1 V. The leakage current was extremely weak and
remained of the order of 10-9 Acm-2 at 70°C and 500 V reverse bias. 4% of the diodes reached the
theoretical voltage breakdown that was 1030 V. The surface roughness of un-implanted and
implanted regions after diode processing was, respectively, 2 nm and 12 nm.
Observation of Thermal-Annealing Evolution of Defects in Ion-Implanted 4H-SiC by Luminsescence
Authors: Freitas Jaime A. , Jones Kenneth A. , Derenge Michael A. , Vispute R.D. , Hullavarad Shiva S.
Published: March 2009

4H-SiC samples implanted at 600°C with 1020 cm-3 of B or B and C to a
depth of ~0.5 μm, capped with (BN/AlN), and annealed at temperatures ranging from
1400°C – 1700°C were studied using variable temperature cathodoluminescence. New
emission lines, which may be associated with stacking faults, were observed in the
samples co-implanted with B and C, but not in the samples implanted only with B.
For both the B and B and C co-implanted samples, the intensity of the line near 3.0 eV
decreases with increasing annealing temperature, TA, and this line is not observed
after annealing at 1700°C. The D1 defect related emission lines are observed in the
luminescence spectra of all samples and their relative intensities seem to vary with the
implantation-annealing schedule and excitation conditions.
Die Bonding Issues on Silicon Carbide Diodes
Authors: Lee Seung Yong , Lee Jang Sub , Kim Tae Hong , Choi Sung Yong , Kim Hak Jong , Bahng Wook , Kim Nam Kyun , Lee Sang Kwon
Published: March 2009

We report on the die bonding processes and how the surface roughness and metallization
schemes affect the processes of die bonding in 4H-SiC device fabrication using a soldering test and
die shear test (DST) with differently prepared 4H-SiC samples. The first set of samples (FZ#1 and
FZ#2) was capped with sequentially evaporated Ti and Au on an annealed Ni layer. The second set of
samples (FZ#3 and FZ#4) and the third set of samples (FZ#5 and FZ#6) were prepared by 4μm-thick
Au electroplating on an annealed Ni layer and an un-annealed Ni layer, respectively. The quality of
the soldering, such as the solder coverage, void, and adhesion, was characterized by optical
microscope, X-ray microprobe, and DST. We found that the samples (FZ#4 and FZ#6) deposited by
Au electroplating on C-face (bottom-side) 4H-SiC provided a satisfactory result for the tests of solder
coverage, void, and DST and also realized the cleaning process prior to the electroplating and
soldering was the most crucial in the die packaging processes of vertical structure devices. The void
fraction measured by X-ray microprobe for the samples, FZ#4 and FZ#6 was 2.2% (average for 5
samples) and 0.8% (average for 3 samples), respectively.
Ohmic Contacts on p-Type SiC Using Al/C Films
Authors: Lu Wei Jie , Landis G.R. , Collins W.E. , Mitchel W.C.
Published: March 2009

Al based alloys, such as Ti/Al, are commonly used for ohmic contacts on p-type SiC.
The interfacial structures of a metal alloy film on SiC are very complicated after annealing. Al is
considered as the key element responsible for forming ohmic contacts on p-type SiC, and reacts
with C from SiC and forms Al4C3 and Si during annealing. In this study, we have investigated
ohmic contact formation of a single component Al4C3 film on p-type SiC. Based on the
stoichiometric formation of Al4C3 between Al and C at high temperatures, several samples with
various Al/C mole ratios have been examined for ohmic contact formation after different annealing
temperatures. Carbon rich and stoichiometric Al4C3 films form ohmic contacts on p-type 4H-SiC
(~2.8 x1018 cm-3 ) after annealing at 800 and 900°C. X-ray diffraction (XRD) data have shown that a
single component Al4C3 is formed when an ohmic contact on p-type SiC is activated. Al/SiC, as the
control sample, does not form ohmic contacts under the same conditions. This study reveals that
Al4C3 can be responsible for forming ohmic contacts on p-type SiC. However, its chemical
instability requires that the secondary metal is necessary to form stable ohmic contacts when Albased
films are used.
Evaluation of Schottky Barrier Height of Al, Ti, Au ,and Ni Contacts to 3C-SiC
Authors: Satoh Masataka , Matsuo H.
Published: March 2009

The Schottky barrier height (SBH) of Al, Ti, Au, and Ni contacts to n- and p-type 3C-SiC
is investigated by means of I-V and C-V measurements. All metal contacts to n- (net donor
concentration: 1.0 x 1016 /cm3) and p-type (net acceptor concentration: 4 x 1016 /cm3) 3C-SiC show
the rectifying I-V characteristics except for Al contact to n-type 3C-SiC. Only Al contact to n-type
3C-SiC shows the ohmic characteristics. As the work function of metal is increased from 4.3 (Ti) to
5.2 (Ni) eV, SBH for n-type 3C-SiC is increased from 0.4 to 0.7 eV and SBH for p-type 3C-SiC is
decreased from 2.2 to 1.8 eV. The small change of SBH for 3C-SiC may be correlated to the crystal
orientation and the defects on the surface of 3C-SiC.
Impact of Dislocations on Gate Oxide in SiC MOS Devices and High Reliability ONO Dielectrics
Authors: Tanimoto Satoshi
Published: March 2009

In this work, it was clarified that many dislocations present on the substrate surface
markedly deteriorated the TDDB property of thermal gate oxide on commercially purchased 4H-SiC
epitaxial substrates. However, it was also experimentally shown that even after removing all of the
dislocations, there was still a significant difference in the charge-to-breakdown (QBD) value between
thermal oxides on SiC and on Si. It was suggested that this difference might partly originate from the
intrinsic physics. The ONO gate dielectric was shown to be a promising alternative to thermal oxide.
Experimental results indicate that the ONO dielectric on 4H-SiC could achieve a higher QBD value
than thermal oxide on Si. A value of QBD = 408 C/cm2 was achieved for an ONO gate dielectric, with
a SiO2 equivalent thickness of 40 nm, on regular 4H-SiC.
Improved 4H-SiC MOS Interfaces Produced via Two Independent Processes: Metal Enhanced Oxidation and 1300°C NO Anneal
Authors: Das Mrinal K. , Hull Brett A. , Krishnaswami Sumi , Husna Fatima , Haney Sarah K. , Lelis Aivars J. , Scozzie Charles , Scofield James D.
Published: March 2009

Two previously reported MOS processes, oxidation in the presence of metallic
impurities and annealing in nitric oxide (NO), have both been optimized for compatibility with
conventional 4H-SiC DMOSFET process technology. Metallic impurities are introduced by
oxidizing in an alumina environment. This Metal Enhanced Oxidation (MEO) yields controlled
oxide thickness (tOX) and robustness against high temperature processing and operation while
maintaining high mobility (69 cm2/Vs) and near ideal NMOS C-V characteristics. Raising the NO
anneal temperature from 1175oC to 1300oC results in a 67% increase in the mobility to 49 cm2/Vs
with a slight stretch-out in the NMOS C-V. Both processes exhibit a small 30% mobility reduction
in MOSFETs fabricated on NA = 1x1018 cm-3 implanted p-wells. The low field mobility in the
MEO MOSFETs is observed to increase dramatically with measurement temperature to 160 cm2/Vs
at 150oC.
High Temperature Erosion-Oxidation Behavior of Thermally Sprayed NiCr Based Alloy and Cermets Coatings
Authors: Kunioshi Clarice Terui , Correa Olandir Vercino , Ramanathan Lalgudi Venkataraman
Published: March 2009

The erosion-oxidation (E-O) behavior of high velocity oxy fuel (HVOF) sprayed Ni20Cr alloy as well as WC and Cr3C2 cermet coatings on a steel substrate were studied. The E-O tests were carried out in a rig with specimen assemblies that were rotated through a fluidized bed of erodent particles in the temperature range 500-850°C and with erodent impact velocities of 2.5-19.5 ms-1. Alumina powder (~200Am) was used as the erodent. The E-O resistance of the coatings was determined as wastage, as a function of temperature. The three coatings did not exhibit any significant change in E-O at temperatures up to 500-600°C. At higher temperatures, wastage increased with temperature, reached a maximum at 700°C and then decreased with further increase in temperature. Different E-O regimes were identified. The specimen surfaces were examined in a scanning electron microscope and their roughness determined. E-O maps have been drawn that define conditions under which the coatings undergo low, moderate and severe wastage.