Structural calibration of tensile-strained GaAs/InAlAs quantum wells

A set of novel lattice-mismatched quantum-well structures is investigated. These samples are composed of tensile-strained GaAs double quantum wells co ntained within relaxed InxAl1-xAs layers which are lattice mismatched with the GaAs substrate. The in-situ calibration of the alloy composition and gr owth rate by reflection high-energy electron diffraction (RHEED) is compare d with ex-situ characterization techniques which include double-crystal X-r ay diffractometry and transmission electron microscopy (TEM). Further analy sis of the sample structure is performed using Taupin-Tagaki equations base d on dynamical scattering theory. Generally, the postgrowth characterizatio n results suggest that RHEED oscillation calibration is still an effective tool for the material system used in this research to obtain information on growth rates and alloy composition. However, it is noticed that the In mol e fraction determined by X-ray diffraction has a deviation from predicted v alues by RHEED oscillation. This deviation was ascribed to the strain effec t on the incorporation of indium atoms. (C) 2001 John Wiley & Sons, Inc.