Observation of strain distributions in partially relaxed In0.2Ga0.8As on GaAs using electron channelling contrast imaging

Electron channelling contrast imaging (ECCI) has been used to image misfit dislocations between single epitaxial layers (epilayers) of In0.2Ga0.8As grown on GaAs (001). Bulk specimens of the as-grown material were examined over a range of epilayer thickness from 25 to 3000 nm. Spectral analysis of ECCI intensity traces was used to establish whether strain fields from the individual dislocations overlapped. Significant overlapping of strain fields was first observed at an epilayer thickness of 100 nm which corresponds well to the onset of macroscopic strain relaxation.