X-RAY CHARACTERIZATION OF VERY THIN GAXIN1-XP (X-APPROXIMATE-TO-0.5) LAYERS GROWN ON INP

High resolution X-ray diffraction has been successfully used to study structural configuration of very thin GaxIn1-xP (x approximate to 0.5) embedded in InP, grown by low-pressure metal-organic vapor-phase epit axy. Both superlattice and single-strained-layer structures with vario us Ga0.5In0.5P layer thicknesses were investigated. The layer thicknes s, composition and interface grading have been determined. A graded Ga xIn1-xP film was identified in the Ga0.5In0.5P-InP upper interface of all samples presented in this paper, while the lower interface is kept relatively sharp. Our observation can be explained by Ga-component se gregation from the Ga0.5In0.5P layer into the following InP layer. The dependence of the dimension of graded interlayer on Ga0.5In0.5P thick ness and the growth rate of Ga0.5In0.5P film in the range of coherent growth were evaluated. It is shown that the X-ray diffraction method c ombined with the computer simulation based on the dynamical diffractio n theory is a sensitive tool to study not only uniform but also graded layers quantitatively. Scanning transmission electron microscopy meas urements were carried out for comparison, clearly proving the X-ray re sults.