CHARACTERIZATION OF INTERFACE STRUCTURE IN GAINAS/INP SUPERLATTICES BY MEANS OF X-RAY-DIFFRACTION

Ga-In-As-P/InP superlattice structures grown by low-pressure metalorganic vapour phase epitaxy (LP-MOVPE) were analysed with high-resolution X-ray diffraction (HR-XRD). The XRD pattern of a Ga0.46In0.54As/InP multiple quantum well sample shows up to two orders in magnitude more intensity than is expected according to a simulation assuming abrupt transitions. The strong intensity of the high order satellite peaks is explained with a simple model based on discontinuity in the lattice constant at the interfaces themselves. Remaining deviations lead to the assumption of compositional grading near the interfaces. A carry-over of As into InP as well as of P into GaInAs on a scale of some nm can clearly be shown, whereas no hints for comparable problems with the group III elements are found. The results show the great sensitivity of X-ray diffraction to compositional changes when strain occurs.