Localized perturbations in si-ge strained layers grown by mbe the ‘pagoda’ defect

Abstract

The nature and origin of a new type of defect in strained layer Si₁−_xGe_x-Si structures grown by molecular beam epitaxy (MBE), the ‘pagoda’ defect, has been studied by electron microscopy. The defects are visible both by structure factor and strain contrast. They are found to propagate in a direction determined by the position of the Si source in unrotated substrates, and to have their origin in the role played by SiC particles (left after cleaning the substrate) during the growth process. Pits that form at the SiC particles are preserved during MBE growth and perturb the strained layers, leading to the formation of pagodas.