Direct Observation of Stress Relaxation Process in 4H-SiC Homoepitaxial Layers via <i>In Situ</i> Synchrotron X-Ray Topography

Abstract

During 4H silicon carbide (4H-SiC) homoepitaxy and post-growth processes, the development of stress relaxation has been observed, in which interfacial dislocations (IDs) are formed at the epilayer/substrate interface, relaxing the misfit strain induced by the nitrogen doping concentration difference between the epilayer and substrate. It is widely believed that an interfacial dislocation is created by the glide of a mobile segment of a basal plane dislocation (BPD) in the substrate or epilayer towards the interface, leaving a trailing edge component right at the interface. However, direct observation of such mechanisms has not been made in SiC before. In this work, we present an in situ study of the stress relaxation process, in which a specimen cut from a commercial 4H-SiC homoepitaxial wafer undergoes the stress relaxation process during a high-temperature heat treatment while sequential synchrotron white beam X-ray topographs were recorded simultaneously. Based on the dynamic observation of this process, it can be concluded that thermal stress plays a role in the relaxation process while the increased misfit strain at elevated temperature most likely drives the formation of an interfacial dislocation.

Effect of dislocations on carrier recombination and photoelectrochemical activity in polished and unpolished TiO2 and SrTiO3 crystals

“…45 In 4H-SiC, the heightened misfit strain at elevated temperatures is likely a driving factor in the formation of interfacial dislocations. 46 Furthermore, strain can also affect the dislocation formation energy, with tensile or compressive strain favoring or hindering dislocation formation in SrTiO 3 . 47 Moreover, dislocations are primarily induced by thermal stresses resulting from temperature gradients during the liquid encapsulated Czochralski (LEC) growth process in III-V semiconductor substrates.…”