Abstract: The origin of dislocation evolution during SiC crystal growth is usually related to lattice
relaxation mechanisms caused by thermal stress. In this paper we discuss dislocation generation and
dislocation propagation related to doping and suppression of basal plane dislocations, the latter
being of particular interest for bipolar electronic devices. We have prepared alternating p-/n-/pdoped
SiC crystals using the donor nitrogen and the acceptors aluminum or boron. In addition we
determined the mechanical properties of n-type and p-type SiC; in particular we measured the
critical shear stress by nano-indentation on c-plane and a-plane 6H-SiC surfaces. A considerably
lower basal plane dislocation density is found in aluminum as well as in boron doped p-type SiC
compared to nitrogen doped n-type SiC. It is concluded that the explanation of the reduced basal
plane dislocation density in p-type SiC needs the consideration of electronic as well as mechanical
Abstract: In this paper we report, based on analysis of dislocation statistics, on the influence of
growth temperature on the nucleation, propagation and annihilation mechanisms of dislocations.
Using KOH defect etching and optical microscopy we have conducted dislocation tracking along
lengths of crystals grown under various process temperature regimes to study their evolution and
propagation mechanisms statistically. We further present the influence of growth temperature on the
step structure of the growth front using AFM measurements. From the analysis of dislocation statistics
and step structure in relation to temperature we derive the role of surface kinetics of the SiC gas
species on the growth surface in dislocation evolution during PVT growth of bulk SiC.
Abstract: Synchrotron reflection X-ray topography and KOH etching were applied to investigate the
effects of the ion implantation/annealing process on the existing dislocations in the 4H-SiC epilayers
and second epitaxial growth on the ion implanted layer. No systematic generation of dislocations or
stacking faults caused by the second epitaxial growth on the implanted layer was observed, while
BPDs were confirmed to migrate in the epilayer during the implantation/annealing process. The BPDs
bend markedly near the bottom of the implanted layer and tend to lie along the <1-100>
(perpendicular to the off-cut direction) after the implantation/annealing process. The lattice mismatch
strain created by the implantation is a possible driving force of the glide motion of the BPDs.
Abstract: The advantage of room-temperature photoluminescence (PL) mapping was demonstrated
for nondestructive detection of stacking faults (SFs) in off-oriented 4H-SiC epitaxial and bulk wafers.
In mapping of the SF-related emission at 2.9 eV on the wafers, the SFs in the surface region appeared
as a bar-shaped pattern with the long side perpendicular to the off-cut direction. The use of 266 nm
light excitation is essential to detect the SF pattern in the bulk wafers because of its shallow
penetration depth. The dark lines crossing the bar-shaped patterns in the epitaxial wafers are
ascribable to the basal plane dislocation located close to the SF-planes.
Abstract: First-principles calculations are used to investigate the partial dislocations in 4H-SiC. We
have shown that the Peierls barriers are strongly dependent on the dislocation core structures. Our
results have revealed that the asymmetric reconstruction does not possess midgap states while the
symmetric reconstructions, characterized by dangling bond on like atoms along the dislocation line,
are always electrically active. We suggested that under forward bias, the free energies of the
symmetric reconstructions are dynamically lowered by continuous electron-hole transitions between
the respective deep levels and valence/conduction bands.
Abstract: By the use of Cl2-O2 thermal etching method, the etching rates of 4H-SiC were reached
to about 1μm/h for Si and 40μm/h for C face at 950oC. Etch pits only appeared over 0.25-μm-etched
depth on the 4H-SiC (0001) Si face. The shapes and density of etch pits are similar tendencies in the
case of molten KOH etched surface. To study the relationship between thermally etched surface
features and crystal defects, the planar mapping electron-beam-induced current (EBIC) technique
was carried out. Almost dark areas in the EBIC image correspond to the etch pits. From the EBIC
image, a shell-like pit formed by the Cl2-O2 etching on the (0001) Si face is a basal plane
Abstract: Using TEM we show that defective regions are formed in SiC by ion implantation, and
that some of the regions grow at the expense of others. Using HRTEM we show that these regions
contain a large number of stacking faults. It is proposed that these stacking faults are Frank
intrinsic stacking faults formed by condensation of divacancies, and it is this defect that is
associated with the DI defect.
Abstract: Device quality SiC wafers are extremely expensive and available from only a limited
number of vendors. This has limited the ability of researchers to compare and evaluate quality from
various vendors. This paper surveys some properties and characteristics of SiC wafers purchased in
the commercial market place and describes the product variability among vendors as a method to
highlight the areas where improvements in substrate quality are desirable.
Abstract: A non-destructive technique to image the dislocations and other extended defects in SiC
epitaxial layers has been developed. Basal plane dislocations (BPDs) and threading dislocations
(TDs) are imaged. Photoluminescence from the dislocations is excited with the 364 and/or 351 nm
lines of an argon ion laser and near-infrared light is collected. A computer controlled probe station
takes multiple images and the mm-sized images are stitched together to form whole-wafer maps.
The technique is applied to a set of four n+ wafers from the same boule with 50 um n- epitaxial
layers. The epitaxy was grown with Cree’s low-BPD process. BPDs form as either single, isolated
dislocations or as clusters encircling micropipes. The concentration of TDs is on the order 104/cm2
and the local concentration varies more than an order of magnitude. The advantages of mapping
dislocations by UV-PL imaging compared to other techniques are discussed.