Phase-change characteristics of carbon-doped GeSbSe thin films for PRAM applications

Phase-change random access memory (PRAM) is a promising way to overcome problems associated with dynamic random access memory and flash memory, namely, scaling them down to meet increasing performance and reliability demands. Herein, we evaluate carbon-doped Ge₁₀Sb₉₀Se₈ (GSS-C) as a potential chalcogenide material for PRAM. The carbon-doping effects on the physical and electrical properties of GSS film were investigated at carbon concentrations from 0 to 11 at.%. The crystal structures were analyzed via X-ray diffraction, which demonstrated that the undoped GSS films had multiple phases; however, incorporating carbon led to a single phase with a rhombohedral crystal structure (Sb phase). The grain size and change in thickness upon phase transition both decreased with increasing carbon concentration, whereas the crystallization temperature and sheet resistance of the amorphous and crystalline states increased. X-ray photoelectron spectroscopy revealed that adding carbon leads to the formation of C–Ge and C–Sb bonds. Moreover, as the carbon concentration increased, the on/off ratio and optical band gap increased. These results imply that GSS-C possesses advantageous thermal stability, reliability, and electrical properties, which strongly suggest that GSS-C would be a promising candidate for phase-change memory applications.