Investigation of Misfit Dislocation Configurations in Mbe-Grown InGaAs Layers on Misaligned GaAs (001) Substrates

Abstract

The configurations of misfit dislocations in In0.2Ga0.8As/GaAs(001) hetero structures grown on slightly misoriented substrates was investigated by transmission electron microscopy (TEM). Layers 6 nm, 20 nm and 40 nm thick were grown by MBE. The substrate was tilted in [110], [110], [120], [210] and [010] directions at angles between 0° and 10°. Only in the 40 nm thick layers networks of 60° and 90° dislocations were formed. Misfit dislocations were found at the interface in <110> directions. In the substrate tilting range between 0° and 4° the changes in dislocation density can be explained by the differentcharacter of α and β dislocations. For a substrate tilting above 6° the different dislocation sets show an increased anisotropy. The misfit dislocations at the interface were decorated by In atoms. The influence of three-dimensional crystal growth on increasing surface roughness is discussed.