Studies of defect generation in CdZnTe and InP single crystals using synchrotron white beam x-ray topography

Synchrotron White Beam X-ray Topography (SWBXT), along with Lang topography, chemical etching analysis, TEM and Nomarski optical microscopy have been used for the characterization of defect structures in large CdZnTe and InP single crystals and for the determination of the nature of growth striations and the contrast formation mechanism in the images of growth striations in X-ray topography.; In the study of defect structures in CdZnTe single crystals, it was found that dislocations of very high density arrayed in a mosaic pattern were observed in all ground-base samples grown under identical growth conditions with flight samples except for the gravity conditions. Regions of very low dislocation density {dollar}({lcub}<{rcub}1000 rm cmsp{lcub}-2{rcub}){dollar} were observed in wafers sliced from steady-state growth regions solidified without wall contact.; Among the structural defects present in InP single crystals, the most pervasive ones are slip bands. X-ray topography revealed numerous slip bands nucleated from the peripheral regions and propagated into the interior of the crystal. The most likely origins for the formation of these structural defects are attributed to relieve large thermal stresses generated at the point where the hot solid material emerges from the encapsulant. A thermo-elastic finite element stress analysis for an intermediate growth stage also revealed that the maximum excess resolved shear stresses are generated on the outer surface of the crystal at the point where the crystal emerges from the encapsulant.; The growth interface morphology at different stages of a MLEK growth process is characterized through the observation of growth striations in longitudinal cut sulphur doped InP single crystals. Results revealed that the morphology of growth interfaces can be strongly influenced by the growth conditions.; The nature of growth striations as well as the contrast formation mechanisms in the images of growth striations on X-ray topography in sulphur doped InP sing!e crystals are investigated using a combination of various X-ray topographic techniques, TEM and chemical etching analysis. Results suggest that the formation of growth striations is attributed to the segregation of sulphur, which substitutes the atomic sites of phosphorus, leading to the generation of bulk stresses associated with lattice mismatches between layers of different dopant concentration.; Preliminary results in the investigation of twinning in (001) grown InP single crystals revealed a {dollar}{lcub}115{rcub}{dollar} scM-{dollar}{lcub}111{rcub}{dollar} scT orientation on the as-grown outer surfaces of the crystal across a twin boundary. Detailed studies including the local solid-liquid interface morphology and crystallographic orientation relationships revealed that the growth at a conical angle of {dollar}74.2spcirc{dollar} is the most dangerous one from the point of view of initiating twinning.; Back-reflection Laue diffraction patterns recorded from different twinned regions revealed the formation of {dollar}{lcub}110{rcub}{dollar} facets on the as-grown outer surfaces, while the matrix adjacent to the twin boundary is parallel to a {dollar}{lcub}114{rcub}{dollar} plane. (Abstract shortened by UMI.)...