Investigation of LPE Ga 1− xAl xAs/GaAs laser structures by double crystal diffractometry

Abstract

The possibility of characterizing Ga 1− x Al x As/GaAs laser structures, with both a single and double confinement, using the double crystal X-ray diffractometry has been investigated. Simulations, based on the Takagi-Taupin dynamical theory, have shown that the shape of the Bragg peak of the thicker external confining layers exhibits a nearly periodic behaviour as a function of the thickness of the thinner active or internal confining layer; a simple relation between the thickness period and the composition difference of the considered layers has been obtained for the first time. Rocking curves of complex Ga 1- x Al x As/GaAs laser structures grown by low temperature liquid phase epitaxy have been recorded with a suitable experimental set up and the depth variation of the composition x has been successfully determined in double confinement C 1B 1AB 2C 2 laser structures. Small, but significant differences between the layer stack expected from the growth parameters and that obtained by the double crystal method have been revealed. Finally, it has been found that the experimental results are in a very good agreement with those obtained by other techniques.