Analysis of the growth kinetics during high temperature crystal growth of SiC using computed tomography for the in-situ 3D visualization of the growth interface

The project proposal addresses the kinetics of the growth of single crystalline silicon carbide at ca. 2200 °C and makes use of in-situ measurement data of the growth interface acquired by 3D computed tomography. The goal of the project is the derivation of a semi-quantitative model that is able to describe the lateral overgrowth of crystal defects and the enlargement of the single crystalline area during the high temperature vapor growth process. A key role hereby plays the precise knowledge of the location and size of the facet, of the shape of the surrounding crystal surface nearby and its time evolution during the crystal growth process. Modelling will consider the supersaturation of the gas phase in front of the growth interface and the total mass flux. The visualization of the crystal growth interface will be carried out using an in-situ 3D computed tomography measurement technique, which needs major methodological adaptions in the strongly distorted measurement environment. The goal is to retrieve the crystal growth interface (shape, faceting), the changes in the source material (consumption, local phase changes) and inside the growth crucible (dissociation, materials degradation) in three dimensions with a spatial resolution of ca. 75 µm. Special emphasis will be put on the thermal boundary conditions of up to 2700 °C at the hottest point in the growth reactor. The project deals with the hexagonal semiconductor material silicon carbide, however, the derived results are believed to be of general value for the research field of crystal growth.The principle feasibility of the target project was already demonstrated in a simple setup using a combination of a standard crystal growth machine, an x-ray source and detector. The measurement data for the 3D reconstruction of the growing crystal and its surroundings were determined under continuous axial rotation of the growth crucible. Hereby, for the first time the crystal growth interface, as well as changes in the source material and in the crucible, were visualized 3-dimensional at elevated temperatures above 2200 °C. These measurement results, however, exhibit a number of artifacts and errors which will be addressed in the underlying project by adapting the growth setup and developing new algorithms for the improved data analysis.