INGAAS/GAAS STRAINED SINGLE QUANTUM-WELL CHARACTERIZATION BY HIGH-RESOLUTION X-RAY-DIFFRACTION

A series of InxGa1-xAs/GaAs strained single quantum wells (SQWs) grown by the molecular beam epitaxy (MBE) technique, with well thicknesses ranging from 80 to 200 angstrom, In content 0.05 < x < 0.257 and a 400 angstrom thick GaAs cap has been characterized by the double crystal diffraction technique in the conventional 400 Cu Kalpha symmetrical reflection geometry. A careful simulation of the diffraction profiles allowed a determination to be made of the In contents and the thicknesses with an accuracy of 0.5% and 10 angstrom respectively. Even if the measured values were in good agreement with those provided by the reflection high energy electron diffraction oscillations, a small but systematic deviation of the measured compositions towards lower values was observed. The cladding layer thicknesses obtained by a profile simulation procedure were not in agreement with those evaluated by the periodicity observed in the diffraction profiles. Due to the very high sensitivity of the diffraction profiles to the well parameters, the compositions calculated under the assumption of the Vegard law and the elastic deformation of the cell appeared to be significantly affected by the choice of the elastic constants used in the calculation.