Performance studies on Ge1Sb2Te4 thin film devices

Thin amorphous films of Ge₁Sb₂Te₄ (GST) were prepared from their respective polycrystalline bulk on ITO coated glass substrates by a thermal evaporation technique. Thin film devices based on GST for Non Volatile Random Access Memory (NVRAM) applications were studied for 100 nm and 180 nm thickness, using current-voltage measurements. Current-voltage (IV) measurements on Al/GST/ITO/Glass device using voltage sweep mode, confirmed the electrical switching of the material between the amorphous and crystalline states. With the threshold voltage of 1.6 V and 2.1 V for 100 nm and 180 nm thickness. More than three orders of resistance differences existed between the amorphous state and the crystalline state. The variation of the resistance with time at both SET and RESET state resistance after a year was insignificant, confirming the nonvolatile nature and the reliability of the GST device. Stress test for GST, with SET and RESET resistance in each cycle was read at 1 V for more than 1000 continuous switching cycles.