Microsize defects in InGaAs/GaAs [formula omitted]A/B multilayers quantum dot stacks

Abstract

Surface morphology of microsize defects on the surface of various high-index GaAs substrates was investigated using an atomic force microscope (AFM). The surfaces investigated were the top layer of 1- and 17-period In 0.45 GaAs 0.55 / GaAs structures with quantum dots or buffer layer. These structures were characterized by the formation of oval defects on (1 0 0) surfaces, and microsize defects possessing the shape of multifaceted pits and hillocks on ( N 1 1 ) A / B ( N = 7 , 5 , 4 , 3 ) surfaces. The microsize defects were found to chaotically distribute on the surface and, as a rule, gathering in groups with some number of defects. Their density did not depend on the substrate orientation while the shape and orientation of the microsize defects were found to depend on the crystallographic orientation of the substrate. This dependence was determined to be the result of anisotropy of surface diffusion and surface elastic properties. The anisotropy of elastic properties of high-index surfaces was found to be the dominating factor in determining the microsize defect shape. We also report direct evidence of the fact that the effect of quantum dot lateral ordering observed on high-index ( N 1 1 ) B surfaces is determined by the anisotropy of surface elastic properties as well as elastic interaction between adjacent quantum dots.