INVESTIGATION OF A SEMICONDUCTOR SUPERLATTICE BY USE OF GRAZING-INCIDENCE X-RAY-DIFFRACTION

A GaInAs/InP superlattice with 10 periods grown by a MOCVD technique on [001] InP was measured by X-ray diffraction under grazing incidence. The details of the GID technique are explained and the results on the superlattice real structure are interpreted in terms of a kinematical scattering approach. Because the depth probed by the X-rays is extremely reduced to a near-surface region both the thickness of the supercell (44 +/- 1 monolayers) and of the (GaIn)As quantum wells (2 +/- 1 monolayers) can be determined with monolayer accuracy. By successively increasing the penetration depth of the X-rays, the vertical density profile is probed in different regions below the sample surface. The measurements indicate that the thickness of the solid solution layer varies by about 1-2 monolayers laterally and in depth. The composition of the layers is different from that expected from the growth conditions.