Stress relaxation in highly strained InAs/GaAs structures as studied by finite element analysis and transmission electron microscopy

Finite element (FE) analysis and transmission electron microscopy (TEM) observations have been used to model stress relaxation in InAs quantum dots deposited on (001) GaAs. TEM observations show that these islands are coherently strained and the corresponding strain contrast is simulated using the dynamical electron diffraction contrast theory. The dot strain fields used for the TEM contrast simulations are deduced from FE calculations. These calculations show that elastic stress relaxation mainly occurs at the crest of the island and that the underlying substrate is under tension. That experimental TEM images and simulated images should match shows that the FE method of determination of the dot strain fields is valid (even in the case of microscopic objects), and that the shape of islands can be specified. (C) 1996 American Institute of Physics.