Temperature induced polytype conversion in cubic silicon carbide studied by Raman spectroscopy

Abstract

In this paper, we study the polytype transformation of cubic silicon carbide (3C-SiC) by micro Raman spectroscopy. Two sets of samples are investigated. First, physical vapor transport (PVT) grown samples, grown on chemical vapor deposition (CVD) substrates at growth temperatures between 1800 and 1950°C. The microscopic images of the cross sections and the Raman spectra taken on these grown crystals show a growing fraction of 6H-SiC inclusions with increasing growth temperature. To decide whether these polytype inclusions are induced by the PVT growth process or by the temperature treatment of the CVD substrates, we studied the temperature induced polytype coversion of cubic CVD substrates grown on undulant Si(100) surfaces which were used as seed crystals for the PVT growth. The CVD substrates were annealed in the temperature range between 1700 and 2100°C. The results of this annealing series are similar to the results we find in the PVT grown samples. Therefore we argue that the polytype conversion is not induced by the PVT growth process but a result of the heat treatment of the CVD seed crystals.

Reduction of defects propagating into 3C-SiC homoepilayers by reactive ion etching of 3C-SiC heteroepilayer substrates

“…Compared to the heteroepitaxial growth, significant reductions of the predominant planar defects and protrusions have been expected in 3C-SiC homoepitaxial growth at elevated substrate temperatures much higher than the melting point of Si, 1673 K. Previous homoepitaxial growth studies [2][3][4] were conducted by using freestanding 3C-SiC substrates heteroepitaxially grown on so-called undulant Si(0 0 1) surfaces [5], consisting of the steps with slops in [1 1 0] and [1 1 0] directions. However, significant defect densities were observed in 3C-SiC homoepilayers grown on the heteroepilayer substrates because the defects developing in the substrates were propagated into the homoepilayers.…”

Ultra‐Low‐Temperature Sintering of Nanostructured β‐SiC

“…Al has been reported to dissolve into SiC at and above 1600°C, 12 but the dissolution occurred at 1500°C in this research presumably because SPS method promotes the formation of solid solution 13 . Pure β‐SiC is a metastable phase and was reported to transform into α‐SiC (6H phase) at 1850°C 14 . The low‐temperature phase transformation in this research is believed to be caused by Al which was dissolved in the SiC grains because Al was reported to promote the β‐to‐α phase transformation of SiC 10 .…”

Kinetics of the 3C-6H polytypic transition in 3C-SiC single crystals: A diffuse X-ray scattering study

“…A similar observation has been made by Raman scattering on similar crystals. 14 The activation energies for both mechanisms have been obtained from an Arrhenius plot of the data recorded from the second set of crystals (wafer 2): ln(x) (where x corresponds to either s or x t ) is plotted vs. 1/T (Fig. 5).…”

“…This lack of experimental data regarding the 3C-6H polytypic transition in single crystals is due (1) to the above-mentioned difficulties to grow 3C-SiC single crystals and (2) to the lack of quantitative characterization tools that would allow to obtain quantitative information concerning the transformation (transformation level and polytype volume fraction). Qualitative information, for instance regarding the transformation mechanism or the nature of the polytypes that are formed, have been obtained using TEM, 12 Raman scattering, 13,14 or x-ray rotation photography. 15 Besides, these studies reached contradictory conclusions concerning the transformation mechanism.…”