Synchrotron white beam x-ray characterization of growth defects in bulk compound semiconductors

Structural defects and their distributions in bulk II–VI and III–V compound semiconductor crystals grown by different methods under different growth conditions were characterized by synchrotron white beam x-ray topography (SWBXT) and complemented by high resolution triple axis diffraction (HRTXD), optical microscopy and chemical etching techniques.; In comparison with ground truth samples, Cd_0.96Zn_0.04 Te boules grown in microgravity by the Bridgman method exhibited a lower overall dislocation density but dislocation distribution was heterogeneous with a strong dependence on dislocation types involved, amount of wall contact, location of twinned regions and the high post-solidification cooling rates used. High mobilities of Te(g) type dislocations compared to Cd(g) (or Zn(g)) type and screw dislocations lead to different extents of deformation under equal stress levels while non-uniform wall contact produces higher stress levels in regions of wall contact. Combination of these two effects produced asymmetrically distributed deformation structures in microgravity grown crystals.; Hg_0.8Cd_0.2Te crystals grown by the traveling heater method (THM) in a rotating magnetic field (RMF) exhibit compositional inhomogeneities, strains and high dislocation densities. By correlating with a thermo-solutal model, observed defect distribution is shown to be the result of a complex flow pattern in the solvent zone produced by the competing phenomena of buoyancy-driven and RMF-induced convection.; In PVT grown ZnSe boules, defect distribution is strongly influenced by seeding and gravity vector orientation with respect to growth direction. Occurrence of twinning indicates a tendency to maintain the approximate growth axis perpendicular to the {lcub}111{rcub} planes.; A novel experimental technique—synchrotron white beam x-ray anomalous scattering has been developed. This technique uses the naturally collimated synchrotron white beam to record diffracted intensities continuously as a function of wavelength and can thus map the intensity variation across the absorption edge. Using this technique, the absolute polarity of the {lcub}111{rcub} planes in LEC-grown InP has been determined. Formation of edge facets and the nucleation of twins in LEC-grown InP boules has been found to occur preferentially on {lcub}111{rcub}_P faces and this is attributed to their lower surface energies.