DEPTH SELECTIVE ANALYSIS OF BURIED SEMICONDUCTOR LAYERS USING X-RAY GRAZING INCIDENCE DIFFRACTION. U. Pietsch, D. Rose, Institute of Solid State Physics, University of Potsdam, Germany

The X-ray grazing incidence diffraction method (GID) is a powerful tool to investigate crystalline near suface regions in the depth between 5 and 400 nm. The method was applied on a number of GaAs/(GaIn)As/GaAs[001] single quantum well structures prepared by MOVPE. The thickness of the buried SQW was varied between one monolayers and 5 nm. The experiment was performed at the D4 beamline at HASYLAB using [[lambda]] [[circleplus]] 1.33 Å. At the angular position of the in-plane (200) reflection and setting the angle of incidence [[alpha]]_i fixed the intensity distribution of the diffracted beam was recorded as a function of the exit angle with respect to the sample surface, [[alpha]]_f, (crystal truncation rods - CTR) using a position sensitive detector. Besides the "surface peak" at [[alpha]]_f = [[alpha]]_c (critical angle of total external reflection), CTR- oscillations appear which measure the thickness of the GaAs top layer. As verified by computer simulation the modulation contrast depends on the thickness of the SQW and the perfection of the GaAs/InAs interfaces. Recording CTR's at different [[alpha]]_i the indium concentration can be obtained as a function of depth. We found that none of the samples had sharp interfaces. The indium atoms are spread over 3 -5 monolayers. They occupy the sites along 2D terraces. For thicker SQW (5 nm) we could verify that at least one of both interfaces is graded but the other remains sharp.

The project was supported by the BMBF, grant number 05 5IPAAI 8.