The investigations of characteristics of GeSe thin films and selector devices for phase change memory

Abstract

Ovonic threshold switching (OTS) selector is a key technology for high-density crossbar memory array. The basic characteristics of GeSe OTS material including structural information, film properties, microscopic properties, and electrical threshold switching behaviors are investigated by combining ab-initio molecular dynamics and experiments. Amorphous GeSe contains numerous GeSe covalent bonds and defective structure motifs. The original resistance is extremely high compared to phase change materials, leading to lower leakage currents in device cells. The structure of GeSe remains stable at ∼350 °C and transforms to orthorhombic phase at higher temperature up to 450 °C. The severe phase separation of 500°C-annealed GeSe is observed with Se crystal grains. The high threshold voltage (>4 V) and holding voltage (>1 V) with large fluctuation (>1 V) are presented in the OTS cells with GeSe material. Due to the comprehensive investigations of GeSe material, we can improve the thermal stability and device performance of GeSe as a base material to find promising candidates for crossbar memory.