Contact Resistance-Dependent Phase Change Memory Switching Behaviors in GeTe and Ge2Sb2Te5 Nanowires

Abstract

Phase change random access memory(PCRAM) using chalcogenide materials, which can be reversibly switched between crystalline and amorphous states, is a promising candidate as a flash memory replacement due to its high-speed switching, excellent scalability, long lifetime, and nonvolatility. However, the realization of PCRAM is still limited due to several requirements. The major bottleneck for achieving high density PCRAM is the large reset currents needed to change the phase change material from crystalline to amorphous state.Recent studies have provided that a line cell structure PCRAM with nanowire and a resistive interfacial layer between phase change material and electrode contact can be solutions to reduce the reset current.Here I fabricated GeTe and Ge2Sb2Te5 nanowire phase change memory devices and obtained general switching behaviors of phase change memory. The diameter dependence of phase change memory switching behaviors was studied and a reduction of reset currents with decreasing diameter was observed. Particularly, the contact resistance dependent switching behavior is studied in the nanowire phase change memory devices. The reset current is dramatically reduced with increasing the contact resistance of nanowire phase change memory devices. Ultra-low reset current (36μA) is taken from a GeTe nanowire phase change memory device which has a very high contact resistance of 167kΩ. Results show that contact resistance is an important parameter and must be studied more to improve the switching characteristics of nanowire-based PCRAM.