Influence of Growth Interruption on the Formation of Solid-state Interfaces

In this study the effects of growth interruptions on the formation of the interfaces in GaAs/AlAsmultilayers are investigated. For that purpose a series of different samples has been manufactured with molecular beam epitaxy (MBE). The introduction of growth interruptions of 50 s after the deposition of the layer leads to a change in the morphological properties of the interfaces, in particular their correlation length. These modifications due to the growth interrupt are analysed with diffuse X-ray scattering (DXRS). As a result of the measurements an extension of the lateral correlation length can be proved. By contrast the vertical correlation of the interfaces is not affected. Introduction With the shrinking of the dimensions of solid-state systems its physical properties become more and more influenced by the structure of the interface. Diffuse X-ray scattering (DXRS) is sensitive to the morphological aspects of the interfaces in thin film systems. The diffusely scattered Xrays are detected in the vicinity of the critical angle of reflection. The variation of the scattered radiation is mainly due to the roughness of the interfaces. Because of the small incident (αi) and exit angles (αf) the resulting scattering vector q is very small, and the Laue condition for constructive interference is only fulfilled for the interfaces of the super lattice. The coplanar scattering geometry (cf. fig. 1) used in this experiment causes a zero qy component of the scattering vector q. The qxand qz-components are adjusted by the two angles αi and αf with respect to the sample surface. The intensity profile of the scattered X-rays at the reciprocal coordinates (qx, qz) is the image of the interfaces into the reciprocal space (cf. Fig. 1, right). The areas shaded in grey are not accessible for measurements due to the fact that one of the angles is below zero. This image is the so-called space map of the sample. The structure of this space map is basically generated by the morphology of the interface. 122 Copyright ©JCPDS-International Centre for Diffraction Data 2006 ISSN 1097-0002