Electrical Resistivity of Liquid Ge2Sb2Te5 in Patterned Nanostructures

Phase change memory devices are based on the electrical resistivity contrast between the amorphous and the crystalline phases of chalcogenide materials [1]. Since melting is required to amorphize the material, knowledge of the liquid state properties is critical for device design. Ge2Sb2Te5 (GST) is the most studied phase change material. However, the two experimental values reported to date for electrical resistivity of liquid GST (one on a thin film [2], the other in bulk [3]) differ by an order of magnitude. We have extracted the electrical resistivity of liquid GST from single pulse measurements on a large number of encapsulated GST line structures with varying lengths, widths and thicknesses. Each structure is self-heated to melt by the microsecond voltage pulse while voltage and current are monitored using an oscilloscope. The liquid state resistivity is calculated from slopes of liquid state resistance versus 1/width, fitted as a function of length. The results we obtained for the liquid resistivity of GST in nanostructures are close to those obtained from measurements on bulk GST [3]. 1. H. Wong et al., Proc IEEE 98, 2201, 2010. 2. T. Kato and K. Tanaka, Jap. J. Appl. Phys. 44, 7340, 2005. 3. R. Endo et al., Jap. J. Appl. Phys. 49, 5802, 2010.