ELASTIC MISFIT STRESS-RELAXATION IN IN0.25GA0.75AS LAYERS GROWN UNDERTENSION ON INP(001)

Finite element (FE) analysis, scanning tunneling microscopy (STM), ato mic force microscopy (AFM) and transmission electron microcopy (TEM) o bservations have been used to model stress relaxation in In0.25Ga0.75A s 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 c orresponding strain contrast is simulated using the dynamical electron diffraction contrast theory. The ridge (or hole) strain fields used f or the TEM contrast simulations are deduced from FE calculations. Thes e calculations show that elastic stress relaxation mainly occurs at th e crest of the ridges or at the edges of the holes and that the underl ying substrate is also stressed. To our knowledge, this is the first s tudy describing such various sites of elastic stress relaxation in lay ers grown under tension.