Abstract
Synchrotron X-ray topographs of epitaxial laterally overgrown GaAs(ELO) samples are made in both transmission and reflection geometries. Samples grown on GaAs substrates with separated and merged ELO layers are studied. Transmission, transmission section, back-reflection, back reflection section and grazing incidence X-ray topographs are compared. The topographs, complementary to each other, show that the bending of the ELO layers is visible in all geometries, though ELO images are seen in different ways in different geometries. The observed contrast of the ELO layers is explained using a model based on orientational image contrast. A pair of back-reflection section and back-reflection topographs taken subsequently from the same position is required for successful and unambigious interpretation of topographs.
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