A characterization of In_xGa_1-x As/GaAs strained-layer systems using a combination of synchrotron X-ray topography and transmission electron microscopy

A combination of large area plan view transmission electron microscopy (TEM) and white beam X-ray topography has been applied to the investigation of defects in thin film strained layers of In_xGa_1-xAs grown on GaAs (100) substrates. Using a novel lift-off technique to produce large area plan view TEM samples that cover several square millimeters we have demonstrated consistency between images obtained using the two techniques. TEM images and X-ray topographs of interfacial dislocations obtained with the two techniques are presented for In_xGa_1-xAs alloys 36 nm thick with x = 0.085. The results presented here demonstrate the usefulness of white beam X-ray topography for the investigation of the onset of strain relaxation in InGaAs systems. Specialized topograph techniques are described which provide depth-sensitive information which was used to study selectively the stained-layer interfacial region. This eliminates problems with the interpretation of through-thickness projections of defects that are present in the substrate far from the strained-layer interface. Contrast formation mechanisms for this technique are discussed.