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.

I. Introduction

Chalcogenide glasses are a recognized group of inorganic glassy material which contains large percentage of chalcogen elements S, Se or Te [1]. First, Ovshinsky [2] discovered the information storage capacity of chalcogenide materials owing to phase transition phenomenon in 1960s, many researchers have focused on exploiting the phenomenon. During last decade, Chalcogenide (ChG) based Phase change memory (PCM), is receiving large interest as next generation nonvolatile memory due to its possibility in combining the desired attributes of an ideal memory, such as non-volatility, high endurance, low write/erase power, high speed, high density [3]–[4] and compatibility with standard complementary Metal-oxide-semiconductor (CMOS) technology [5].