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Paper Title Page
Abstract: Recent reports on the impact of elementary dislocations on device performance and
reliability suggest not only micropipe defects but also dislocations should be reduced or eliminated
perfectly. This paper presents bulk growth process for reduction of the dislocations, and quality of the
crystals grown by the process. Etch pit density of the best crystals grown by the process was lower by
three orders of magnitude than that of conventional crystals. Moreover, large diameter crystals (>2”)
with low dislocation density were successfully grown by the process.
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Abstract: The defect distribution in 4H-SiC single crystals in dependence on the seed polarity and
its off-orientation was investigated by KOH-etching, optical microscopy and X-ray topography.
Micropipe density, stacking fault density and dislocation density were determined for 2” crystals
grown in <000-1> direction 0 - 7° off towards <11-20> and for crystals up to 1” in diameter grown
in <11-20> or a- and <1-100> or m-directions and using repeated a-face growth. For the growth in
polar directions the micropipe density and dislocation density decrease with increasing offorientation
of the seed. A similar behavior was found for the stacking fault density and dislocation
density in non-polar directions with off-orientation to c-direction. Nevertheless, while the
dislocation density could be reduced up to three orders of magnitude for the growth along non-polar
directions, the stacking fault density was continuously increasing. Additionally, the defect
distribution after repeated a-face growth will be discussed in terms of growth related and kinetic
models.
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Abstract: The ability to set and accurately control the desired growth conditions is crucial in order
to attain high quality bulk growth of Silicon Carbide (SiC), especially when the ingot size is large
(> 2” in diameter by > 2” long). However, these two aspects of SiC PVT (Physical Vapor
Transport) growth technology are severely limited in “conventional” SiC PVT growth reactors with
single cylindrical heaters. To overcome such shortcomings, an “alternative” furnace design with
two plane resistive heaters is proposed. In order to verify benefits of this design, numerical
modeling and comparative procedures have been employed. Detailed comparative analysis revealed
two fundamental disadvantages of the conventional furnace design, attributed to (a) – significantly
higher in magnitude and spatially nonuniform distribution of the thermal stress that consequently
deteriorates structural quality of the growing SiC boule, and (b) – inability to grow long (> 2”)
monocrystalline ingots of SiC. Furthermore, the potential of the alternative furnace design to
overcome fundamental limitations of the conventional design is also analyzed, with particular
attention being paid to the processes of source material recrystallization.
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Abstract: A novel approach to the high growth rate Chemical Vapor Deposition of SiC is
described. The Halide Chemical Vapor Deposition (HCVD) method uses SiCl4, C3H8 (or CH4), and
hydrogen as reactants. The use of halogenated Si source and of separate injection of Si and C
precursors allows for preheating of source gases without causing premature chemical reactions. The
stoichiometry of HCVD crystals can be controlled by changing the C/Si flow ratio and can be kept
constant throughout growth, in contrast to the Physical Vapor Transport technique. HCVD was
demonstrated to deposit high crystalline quality, very high purity 4H- and 6H-SiC crystals with
growth rates comparable to other bulk SiC growth techniques. The densities of deep electron and
hole traps are determined by growth temperature and C/Si ratio and can be as low as that found in
standard silane-based CVD epitaxy. At high C/Si flow ratio, the resistivity of HCVD crystals
exceeds 105 _cm. These characteristics make HCVD an attractive method to grow SiC for
applications in high-frequency and/or high voltage devices.
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Abstract: Growth rates and relative stability of 6H- and 4H-SiC have been studied as a function of
growth conditions during Halide Chemical Vapor Deposition (HCVD) process using silicon
tetrachloride, propane and hydrogen as reactants. The growth temperature ranged from 2000 to 2150
oC. Silicon carbide crystals were deposited at growth rates in the 100-300 μm/hr range in both
silicon- and carbon-supply limited regimes by adjusting flows of all three reactants. High resolution
x-ray diffraction measurements show that the growth on Si-face of 6H- and C-face of 4H-SiC
substrates resulted in single crystal 6H- and 4H-SiC polytype, respectively. The growth rate results
have been interpreted using thermodynamic equilibrium calculations.
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Abstract: 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.
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Abstract: Growth of 4H-SiC bulk crystals on 4H-SiC {03-38} seeds was done. 4H-SiC {03-38} is
obtained by inclining the c-plane toward <01-10> at a 54.7 degrees angle. Growth on the 4H-SiC
{03-38} seed has the potential to achieve high quality crystals without micropipes and stacking faults.
Micropipe-free c-plane 4H-SiC wafers were achieved by growth on the 4H-SiC {03-38} seed. A
transmission X-ray topograph image of the micropipe free c-plane wafer revealed that there are no
macroscopic defects with displacements.
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