Investigation of Bragg surface diffraction in semiconductors and epitaxic structures by reciprocal-space analysis

Bragg surface diffraction (BSD) is a special case of three-beam diffraction, where the secondary beam is scattered in the surface-parallel direction. Under the BSD condition, the surface-detour reflection (secondary plus coupling reflections) transfers some of the secondary-beam intensity into the monitored primary beam. The extinction regime in which such transfer takes place depends on the crystalline perfection of the surface. Based on this fact, the mapping of the BSD profile, in an ω:φ scan technique, has been proposed [Morelhão & Cardoso (1996). J. Appl. Cryst. 29, 446–456] as a method to obtain information on the in-plane crystalline quality of the surface. With the X-ray optics for BSD mapping, the diffracting surface thickness that defines the profile could not be measured or compared with those under conventional Bragg diffraction. In this report, the BSD using a triple-axis diffractometer is investigated. Reciprocal-space mapping of the Bragg reflection (primary reflection) was performed in and out of the BSD condition. It reveals the diffracting surface thickness of BSD in GaAs and Si substrates. The triple axis was also used to investigate the BSD in the SiGe multiple quantum well, and it has demonstrated the existence of effective satellite peaks for such structures.