Peculiarities of Estimating the Optical Band Gap of Thin Films of Phase Change Memory Materials

The method of spectrophotometry with transmission and reflection spectra recording is used to study the peculiarities of estimating the optical band gap in Ge2Sb2Te5 thin films after annealing at different temperatures, in particular, in the temperature range of the phase transition. A significant influence of the spectrum processing algorithm on the obtained results is found. A comparison of experimental data shows that the sheet reisistance, reflection coefficient, and optical band gap change in different temperature ranges during the crystallization process. In particular, changes in the electrophysical properties continue after the completion of the modification of optical characteristics, which indicates the two-stage nature of the crystallization process in Ge2Sb2Te5 films.