Effect of SiC substrate properties on structural perfection and electrical parameters of AlGaN/GaN layers

We have analyzed the effect of volume and surface defects in SiC substrates on the structure and electrophysical parameters of AlGaN/GaN epitaxial heterostructures grown on them. Regions with internal stresses usually induced by carbon rich disk-shaped inclusions have been detected in the initial substrates. We show experimentally that the presence of internal stresses in SiC could affect the microroughness of the epitaxial films in regions grown on the stressed areas. An abrupt deterioration of electrophysical parameters occurs in epitaxial film regions growing above internally stressed areas in the substrate. AlGaN/GaN layers contain impurities delivered to their bulk during epitaxy or preparatory operations.