Elastic misfit stress relaxation in In0.25Ga0.75As layers grown under tension on InP(0 0 1)

Finite element (FE) analysis, scanning tunneling microscopy (STM), atomic force microscopy (AFM) and transmission electron microcopy (TEM) observations have been used to model stress relaxation in In0.25Ga0.75As layers grown under tension on InP(001). Ridges or holes are observed at the free surface, depending on growth conditions. TEM observations show that the In0.25Ga0.75As layers are coherently strained and the corresponding strain contrast is simulated using the dynamical electron diffraction contrast theory. The ridge (or hole) 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 ridges or at the edges of the holes and that the underlying substrate is also stressed. To our knowledge, this is the first study describing such various sites of elastic stress relaxation in layers grown under tension.