NONDESTRUCTIVE ANALYSIS OF STRUCTURAL DEFECTS IN WIDE BANDGAP II-VI HETEROSTRUCTURES

X-ray scattering measurements of wide bandgap II-VI heterostructures s how that stacking faults (which nucleate defects that are responsible for optical degradation of light emitting diodes and lasers) introduce significant levels of diffuse scattering near Bragg reflections of bo th the epitaxial layers and the GaAs substrate. We employed triple axi s x-ray diffraction techniques to investigate stacking fault diffuse s cattering and used cathodoluminescence and transmission electron micro scopy to independently measure the stacking fault density. For compari son, double axis scans from the same samples were largely incapable of detecting the presence of these defects. Measurements taken at differ ent azimuthal positions exhibit different levels of diffuse scattering and the diffuse scattering intensity is related to the stacking fault intensity in each [110] direction, which suggests that this technique can provide a non-destructive assessment of defects present in these systems. For some samples, the ZnSe buffer layer exhibited a tilt with respect to the substrate along a [110] direction; this tilt was great er than the tilt which would be attributed to growing a strained layer on the slightly miscut substrates which were used here.