Physical and electrical characteristics of Ge_xSb_100−x films for use as phase-change materials

In this study, we investigate a GeSb binary phase to be used as a high-speed phase-change material (PCM). In particular, by varying the Ge concentration from 10 at.% to 30 at.%, we study the effects of the PCM composition on the physical and electrical properties of sputtered Ge_xSb_100−x films. The Ge₁₀Sb₉₀ film assumes a crystal trigonal structure (Sb phase); however, phase separation occurs in the films at higher Ge concentrations (i.e., the Sb phase coexists with the crystalline Ge phase). As the Ge concentration increases, the grain size decreases, and the sheet resistances of both the amorphous and crystalline states increase. An increase in the Ge concentration in these GeSb films results in an increase in the crystallization temperature, activation energy, data retention, and band gap. The current–voltage measurements show that the threshold and RESET currents decrease with increasing Ge concentrations. In addition, we discuss the R–V curve, crystallization speed, and programming window. The results indicate that GeSb films possess favorable physical and electrical characteristics and can be used as PCMs in phase-change memory applications.