Structural defects in SiC ingots investigated by synchrotron diffraction imaging

Abstract

4H silicon carbide as-grown ingots were investigated by diffraction imaging using synchrotron radiation. The white beam section topographs obtained for various sample geometries allowed us to reveal structural imperfections before slicing the bulky ingots to the thin wafers used as electronic device substrates. The systematic investigation indicated that the observed inclusions of different polytypes in 4H-SiC ingots are correlated with the 8° off-axis orientation of the seed. These inclusions, formed at the beginning of the crystal growth, provoke planar defects that propagate along the main vertical axis of the cylindrical crystal. New findings permitted us to understand the inclusion formation with the aim to increase the useful volume.

Synchrotron radiography and x-ray topography studies of hexagonal habitus SiC bulk crystals

“…3 High flux and high energy of the x-ray beams available at the European Synchrotron Radiation Facility (ESRF), together with the large beam size, permitted studying the whole volume of the bulky SiC ingots. 2 Moreover, special properties of the third-generation synchrotron sources, like the ESRF, opened the way to novel imaging techniques like phase contrast radiography. 4,5 Being insensitive to strong deformations specific to sublimated grown SiC crystals of large area, this method allowed one to image MPs in samples of any crystalline perfection.…”

Ab initioMethod for Calculating Electron-Phonon Scattering Times in Semiconductors: Application to GaAs and GaP

“…for GaP unveils the strong dependence of the electron-phonon coupling matrix elements on the wave vector of the final electronic state and on the phonon mode. This important result, already pointed out for GaAs [25,30], is nevertheless neglected in most of today's descriptions of the collisional deexcitation processes [10,31]. The integration over all final electronic states required by Eq.…”

Comparative Studies of Carrier Dynamics in 3C-SiC Layers Grown on Si and 4H-SiC Substrates

“…5b) is explained by known scattering mechanisms in SiC. 28,29 At low temperatures (T < 250 K) acoustic phonon scattering is dominant l AC = 9 9 10 5 T À3/2 , whereas at high temperatures (T > 250 K) the influence of polar optical phonon scattering increases l POP = 10 9 [exp(1380/T) À 1], leading to l a $ T À2 dependence, while the impact of ionized impurities is low due to low doping and relatively high temperatures as l ion $ T 3/2 . In our case, the impact of structural defects on mobility is expected to be minor, as scattering at charged dislocations would diminish the mobility at T < 300 K. 30,31 Moreover, the ambipolar mobility values on the front side (low defect density) and on the back side (highly defective area) of the freestanding 3C/Si layer were found to be similar, thus indicating a minor impact of SFs on hole mobility in the T > 80 K range in the given sample.…”