Comparison of Thermal Stability and Electrical Characterization between Ge₂Sb₂Te₅and Ge₁Sb₂Te₄Phase-Change Materials

Abstract

In this paper, thermal stability and electrical characterization of Ge2Sb2Te5 and Ge1Sb2Te4 phase change materials were studied and compared. In-situ electrical resistance measurement at a constant heating rate of 2 K/min shows that Ge2Sb2Te5 takes 510 s for phase change while Ge1Sb2Te4 840 s. Under isothermal condition Ge2Sb2Te5 also crystallizes faster than Ge1Sb2Te4 does. Activation energy of 2.9 and 2.4 eV for Ge2Sb2Te5 and Ge1Sb2Te4 thin films with 30 nm thickness respectively indicates that Ge2Sb2Te5 is more thermally stable in the amorphous state than Ge1Sb2Te4. Ge1Sb2Te4 tends to be more conductive, which was confirmed by its larger carrier concentrations in the amorphous and crystalline states than that of Ge2Sb2Te5 from Hall effect measurement. These results are attributed to the fact that Ge2Sb2Te5 (or written as Ge1.6Sb1.6Te4) contains more Ge atoms substituting for Sb atoms and has less concentrations of vacancies (cavities) than Ge1Sb2Te4 does.