Segregation in InxGa1-xAs/GaAs Stranski-Krastanow layers grown by metal-organic chemical vapour deposition.

Using quantitative high-resolution transmission electron microscopy we studied the chemical morphology of wetting layers in InxGa1-xAs/GaAs quantum dot structures which were optimized for applications to optical devices operating around 1.3 mu m. The samples are grown by low-pressure metal-organic chemical vapour deposition on GaAs substrates. The In concentration profiles of the wetting layers are evaluated with the composition evaluation by lattice fringe analysis method. The profiles reveal a clear signature of segregation. A fit of the profiles with the Muraki et al. model for segregation reveals a segregation efficiency R = 0.65 +/- 0.05 at the growth temperature of 550 degrees C, which is significantly lower than segregation efficiencies observed in samples grown by molecular beam epitaxy at similar temperatures.