Abstract: The effectiveness of room-temperature photoluminescence (PL) mapping was
demonstrated for nondestructive detection of structural defects, such as dislocations, micropipes and
stacking faults, in SiC wafers. PL spectra of bulk wafers were dominated by deep-level emissions
due to Si vacancies, vanadium and undefined centers like UD-1 at room temperature, while those
from epitaxial wafers involved near band-edge emission. We developed a whole-wafer PL intensity
mapping system with a capability of zooming in on the area of interest with a spatial resolution as
high as 1 μm, and showed that the mapping patterns agree well with the etch-pit patterns originating
from the structural defects both on a wafer scale and on a microscopic scale. The intensity contrast
around the defects varied depending on the emission band, suggesting differences in their interactions
with impurities and point defects.
Abstract: A room temperature PL mapping technique was applied to establish the origin of
resistivity variation in PVT-grown 6H SiC substrates. A direct correlation between the native
defect-related PL and resistivity was found in undoped (V-free) samples. In vanadium-doped
samples with low vanadium content, the resistivity showed a good correlation with the total PL
signal consisting of contributions from both vanadium and native point defects. Well-known UD1
and UD3 levels were revealed by low-temperature PL spectroscopy. Some correlation was observed
between these low-temperature PL signatures and the resistivity distribution.
Abstract: Presented is the use of a commercial optical scanner for the mapping of doping density
( ) D N of SiC substrates and as a local probe for D N in different regions. This method provides a
fast and cost effective method for determining D N homogeneity, examining local electrical
characteristics, and recognizing defect sites including areas of different polytypes or
polycrystallinity. Micro-Raman spectroscopy was used to calibrate the transmission intensity with
D N . It is shown that features presented in the calculated D N maps strongly correlate to those
observed in Lehighton resistivity maps.
Abstract: 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.
Abstract: Semi-insulating silicon carbide (SiC) wafers are important as substrates for high
frequency devices such as AlGaN-GaN HEMT’s. A nondestructive characterization technique has
been developed to measure the dielectric properties of SiC wafers in the GHz frequency range
where the devices will operate in order to validate wafers for high yield working devices. The
dielectric loss is measured at approximately 16 GHz in a split microwave cavity. Initial results
show a correlation where the dielectric loss decreases as the resistivity increases, where the
resistivity was measured using a Contactless Resistivity Mapping system (COREMA). The
uniformity of dielectric loss across SiC wafers was evaluated using a split post dielectric resonator
cavity fixed at 5.5GHz to measure the dielectric loss at five points on a wafer. Dielectric loss as a
function of temperature from room temperature to 400°C was also studied.
Abstract: 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.
Abstract: The effects of initial surface morphology on the early stages of porous SiC formation
under highly biased photoelectrochemical etching conditions are discussed. We etched both Si-face
and C-face polished n-type 6H SiC with different surface finishes prepared either by mechanical
polishing or by chemical mechanical polishing at NOVASiC. For both Si-face and C-face porous
SiC samples, a variety of surface and cross sectional porous morphologies, due to different surface
finishes, are observed. The proposed explanation is based on the spatial distribution of holes at the
interface of the SiC and electrolyte inside the semiconductor.
Abstract: Brillouin spectra have been recorded for a series of supported films of p-type
porous 6H-SiC with a branched morphology and porosities in the range from 30% to 58%.
Complex spectra comprising up to 7 identifiable components were observed in some cases.
An effective medium model is being developed as an aid in interpreting the spectra, and
preliminary results are presented.
Abstract: We present relative recovery data for six proteins diffusing through porous silicon carbide
membranes having a hybrid columnar/dendritic morphology. These membranes are promising
candidates for implantable biosensors. The results are interpreted using an effective medium model.