화학공학소재연구정보센터
Journal of Crystal Growth, Vol.244, No.2, 129-135, 2002
Investigation of self-assembled InP-GaInP quantum dot stacks by transmission electron microscopy
Cross-sectional transmission electron microscopy (TEM) studies of vertically stacked InP/GaInP quantum dot (QD) structures have been performed in this work. The specimens were grown by low pressure metal organic vapor phase epitaxy on (0 0 1) GaAs substrates with different misorientation angles toward the next (I I OR plane using the Stranski-Krastanow growth mode. On such substrates, the dots are not perfectly vertically aligned, but show a characteristic lateral shift with respect to the dots of the underlying layer. The angle of the lateral correlation has been determined as a function of GaInP spacer layer thickness, degree of substrate misorientation and growth temperature from TEM micrographs. It points into the opposite direction to the substrate misorientation and increases with decreasing spacer thickness. Molecular dynamics simulations of such structures indicate that the anisotropy of the strain field of these QDs is the main reason for this behavior, whereas the spontaneous ordering of the GaInP matrix does not play a role. (C) 2002 Elsevier Science B.V. All rights reserved.