Morphology, strain and microstructure interrelation in Si-on-sapphire heterostructure

The interfacial region at the substrate, the morphology of the interface and the surface were studied for a number of Si-on-saphire (SOS) samples using X-ray scattering techniques, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). A strained interfacial layer is formed in this high misfit system. The dislocations created in this layer and at the interfacial steps accommodate the elastic strain buildup. The misfit relaxation is accompanied by the misorientation of the epilayer with respect to the substrate, which itself depends on the substrate miscut parameters and the thickness of the epilayer. The observed azimuthal rotation of the epilayer miscut is attributed to the effect of the anisotropic microtwinning evolving with the increasing epilayer thickness. This azimuthal rotation is reflected by the step morphology on the surface of the epilayers.