Determination of the composition profile of HgTe/Cd$_{x}$Hg$_{1-x}$Te quantum wells by single wavelength ellipsometry

An ellipsometric method for reconstruction of the composition profile throughout the thickness in thin mercury-cadmium-telluride nanostructures grown by MBE has been developed. The method is based on ellipsometric data, measured during structure growth and following solution of the inverse ellipsometric problem. For this, a replacement of a part of the inhomogeneous layer by a homogeneous substrate with specially chosen optical constants has been done. Numerical simulation showed the correctness of such replacement and the efficiency of the developed algorithm. Using this method, the active region of the heterostructure consisting of five HgTe quantum wells separated by wide-band CdHgTe spacers has been studied. Using the results of continuous measurements of ellipsometric parameters obtained in situ during structure growth, the composition profiles for all five sequentially grown quantum wells was determined. A high repeatability of the composition distribution through the thickness is shown.