The aim of SiC crystal growing is to produce large and defect-free single crystals. Their quality depends on many parameters, such as the seed crystal, the temperature gradient during the growth process, the quality of the SiC raw material (powder), the evaporation rate of the SiC powder and also the design of the furnace interior of the crystal growing system. The SaxCrystalPower project focuses on these process parameters, their specific influence on the resulting SiC single crystal, and the atomically resolved characterization of the resulting single crystal structures.

The production of high-purity SiC powder is central to the growth of SiC single crystals. This process is extremely complex and has so far only been realized on a pilot plant scale. The powder is introduced into the furnace as a bulk material in order to deposit at high temperatures of over 2000 °C on the seed crystal. For the deposition of larger single crystals, more powder would have to be introduced into the furnace, which is only possible by compacting the powder particles due to the limited furnace volume.

In the SaxCrystalPower project, Fraunhofer IKTS is tackling these challenges and building on the institute's extensive expertise in materials development, powder characterization and sintering processes. In a first step, the influence of particle size and temperature on the formation of certain SiC polytypes is to be investigated experimentally. The synthesized powders will then be examined with regard to their suitability for crystal growth and their possible densification by sintering.

In order to evaluate the resulting qualities of the SiC single crystals fundamentally and for their application as wide bandgap semiconductor substrates, a new high-resolution transmission electron microscope (TEM) is being set up at Fraunhofer IKTS. This new and powerful nanoanalytical technique will enable an investigation of the relationships between technology parameters during sintering and the formation of crystal defects at the atomic level. Another unique feature is that defect densities and defect types in the crystals can be characterized in 3D. This goes far beyond the conventional crystallography of defects in 2D.

In the future, further crystal-growing conditions will be investigated in a new SiC single-crystal growing facility. To this end, the experimentally produced single crystals will be examined in terms of the dimensions achieved, the changes in mass and the crystallographic properties, and the facility will be adapted accordingly. Various measurement methods will be combined to determine the type and density of defects in the single crystals: starting with atomically resolved crystallographic investigations in the TEM, chemical analyses to prove purity and the exact adjustment of dopants, and electrical investigations to measure the charge carrier concentration, the charge carrier type and the charge carrier mobility using Hall effect measurements.

With this work, Fraunhofer IKTS is making valuable contributions to correlations between the properties of SiC single crystals and the corresponding process parameters of the single-crystal growing system. This lays the foundation for promising further developments in SiC single crystal growth. With the acquisition of a new high-resolution TEM, the project also creates a research infrastructure at Fraunhofer IKTS that significantly advances electronics and materials research as a whole.