Electrophysical Properties of Ge–Sb–Te Thin Films for Phase Change Memory Devices

Abstract

In this work, we studied temperature dependences of the resistivity and current-voltage characteristics of amorphous thin films based on the materials of a Ge–Sb–Te system of compositions GeSb₄Te₇ (GST147), GeSb₂Te₄ (GST124), and Ge₂Sb₂Te₅ (GST225) applied in the phase change memory devices. The effect of changes in the composition of thin films on the crystallization temperature, resistivity of films in amorphous and crystalline states, and on the activation energy of conductivity is determined. It is found that the peculiarity of these materials is the mechanism of two-channel conductivity where the contribution to the conductivity is made by charge carriers excited into localized states in the band tails and by carriers of the delocalized states in the valence band.