ELASTIC STRAINS IN GAAS/ALAS QUANTUM DOTS STUDIED BY HIGH-RESOLUTION X-RAY-DIFFRACTION

We have studied a GaAs/AlAs periodic quantum dot array (fabricated by electron beam lithography and reactive ion etching) using high-resolution x-ray reciprocal space mapping around the (004) and (($) over bar 1 ($) over bar 13) reciprocal lattice points. Both the coherently and the diffusely scattered x-ray intensities were analyzed by performing two-dimensional model calculations and comparing them with the measured reciprocal space maps of the diffracted intensity. From the distribution of the diffracted intensities we deduced the average strain status in the dots. From the numerical simulations it is evident that random elastic strain fields are present, which extend through almost the whole volume of the quantum dot. The simulations of the x-ray measurements revealed that the crystalline part of the dots is considerably smaller as scanning electron micrographs would indicate, namely, 50 nm instead of 65 nm, respectively.