The thermal expansion coefficients of the hexagonal SiC polytypes 4H and 6H and with Al and N dopants have been determined for temperatures between 300 and 1770 K. Further, a set of the room temperature lattice parameters in dependence on doping with N, Al, and B has been obtained. Data for the thermal expansion were taken on a triple axis diffractometer for high energy x rays with a photon energy of 60 keV, which allows the use of large single crystals with a volume of at least 6×6×6 mm3 without the need to consider absorption. The room temperature measurements for samples with different dopants have been performed on a four-circle diffractometer. The thermal expansion coefficients along the a- and c-directions, α11 and α33, increase from 3×10−6 K−1 at 300 K to 6×10−6 K−1 at 1750 K. It is found that α11 and α33 are isotropic within 107 K−1. At high temperatures both coefficients for doped samples are ∼0.2×10−6 and 0.3×10−6 K−1 lower than for the undoped material.

A focusing Laue diffractometer for high‐energy X‐rays of up to 300 keV in a laboratory environment is presented. The long attenuation length for X‐ray energies above 50 keV allows for the non‐destructive investigation of structural issues and bulk properties of single crystals. Furthermore, massive sample environments such as high‐temperature furnaces can be used more easily. With an area detector, anisotropic mosaicities or crystallite structure become visible without any rocking movement of the sample.

This paper reviews research on advanced bulk crystal growth of SiC. A brief review highlights the benefits of the so called Modified Physical Vapor Transport Technique which uses an additional gas pipe for fine tuning of the growth cell of a conventional Physical Vapor Transport setup with additional gases. Main emphasis, however, will be laid on a systematic dislocation evolution study for various growth parameter sets. Besides doping, growth temperature was considered. Two main results were found: (i) In p‐type SiC, irrespective of the incorporation of aluminum or boron acceptors, basal plane dislocations that are harmful for bipolar power devices appear less pronounced or are even absent compared to n‐type SiC. (ii) Growth at elevated seed temperature (i.e. 2300 °C and higher) is beneficial for low dislocation densities. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The thermal expansion of 6H Silicon Carbide with different dopant concentrations of aluminum and nitrogen was determined by lattice parameter measurements at temperatures from 300 K to 1575 K. All samples have a volume of at least 6 x 6 x 6 mm3 to ensure that bulk properties are measured. The measurements were performed with a triple axis diffractometer with high energy x-rays with a photon energy of 60 keV. The values for the thermal expansion coefficients along the a- and c-direction, α11 and α33, are in the range of 3·10-6 K-1 for 300 K and 6·10-6 K-1 for 1550 K. At high temperatures the coefficients for aluminum doped samples are approximately 0.5·10-6 K-1 lower than for the nitrogen doped crystal. α11 and α33 appear to be isotropic.

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