The use of superlattices as internal standards for composition and thickness measurements in modulation-doped quantum well structures

Abstract We show that a superlattice introduced in a multilayered structure may act as an internal scale for thickness and composition measurements. The principle of the internal scale procedure consists in determining first the structure of the superlattice by means of conventional X-ray diffraction techniques; the thicknesses determined in this way are then used to calculate the growth rates of the constituting materials which allow us to characterize the entire layer sequence by converting all the growth times into thicknesses. The example of a complex modulation-doped quantum well structure is given as an illustration of the procedure. The agreement between the measurements deduced from diffraction data with those directly obtained using TEM cross-section images demonstrates the efficiency of the internal scale procedure.