Tem Investigation of Self-Organized PbSe Quantum Dots as a Function of Spacer Layer Thickness and Growth Temperature

Abstract

The study of the morphology, lateral and vertical correlation of self-organized PbSe quantum dots in Pb_1-xEu_xTe is presented. The samples consist of quantum dot superlattices of n periods of (PbSe/Pb_1-x Eu_xTe) grown on PbTe/(l 1 l)BaF₂ by the S-K mode using MBE. The Pb_1-x Eu_xTe spacer thickness was varied from 34.3nm to 312nm and the growth temperature was varied between 335°C and 380°C. Our TEM results show very good lateral and vertical correlation of the dots. The dots form an array with either a/b/c/a/b/c/… or a/a/a/… vertical stacking sequence along the [111] growth direction. The stacking sequence is accurately controlled by the thickness of the Pb_1-xEu_xTe spacer layer thickness and the growth temperature. The best a/b/c/… spatial correlation was obtained for temperatures around 380°C and spacer thickness of ~ 40nm. The dots are highly strained and form triangular pyramids with (111) bases and (100) facets as observed by AFM. The shape of the dots also varied with the Pb_1-xEu_xTe spacer thickness. An analysis of the spatial correlation of the dots’ size and shape with respect to spacer thickness and growth temperature is presented.