Effect of doping on the crystallization kinetics of phase change memory materials on the basis of Ge–Sb–Te system

The influence of different amounts of Bi, Ti and In on the thermal properties and crystallization kinetics of Ge2Sb2Te5 thin films for phase change memory devices was investigated. Temperatures and heat effects of crystallization were evaluated for all investigated compositions. Joint utilization of model-free Ozawa–Flynn–Wall and model-fitting Coates-Redfern methods allowed to estimate effective activation energies and pre-exponential factors for crystallization processes of amorphous films as functions of conversion, and determine reaction models. It was found that crystallization process most adequately can be described by the second- or third-order reaction. Storage and data processing times of the phase change memory cells on the basis of investigated materials were calculated with using of determined kinetic triplets of crystallization processes. Calculations showed that crystallization time decreases nearly on the order of magnitude for Ge2Sb2Te5+1 mass% In in comparison with undoped Ge2Sb2Te5. On the other hand, compositions with 0.5 and 3 mass% In allow to increase sufficiently storage time. Introduction of Ti does not significantly affect data processing time of phase change memory cell; however, it decreases storage time. Ge2Sb2Te5+0.5 mass% Bi composition have the most suitable kinetic parameters for phase change memory among the studied thin films.