QUANTIFICATION BY OPTICAL-ABSORPTION OF THE COARSE MODULATION OBSERVED BY TRANSMISSION ELECTRON-MICROSCOPY IN INGAAS LAYERS GROWN ON INP(100)

Optical absorption (OA) and transmission electron microscopy (TEM) hav e been used to analyse and quantify the coarse quasi-periodic contrast observed in InxGa1-xAs layers grown by molecular beam epitaxy on InP( 100) substrates. TEM observations have shown that this coarse structur e arises from a modulation of alloy composition in the epitaxial layer . The energy dispersion in the OA spectra related to the presence of t hese inhomogeneities has been used to quantify the amplitude of the mo dulation. Corrections have been made for the cosinusoidal variations o f the composition. The amplitude of composition modulation is Delta x = 0.6-1.2%. This result agrees with the width of the x-ray diffraction peak.