Atomistic Modeling of Charge‐Trapping Defects in Amorphous Ge‐Sb‐Te Phase‐Change Memory Materials

Abstract

Understanding the nature of charge‐trapping defects in amorphous chalcogenide alloy‐based phase‐change memory materials is important for tailoring the development of multilevel memory devices with increased data storage density. Herein, hybrid density‐functional theory simulations have been employed to investigate electron‐ and hole‐trapping processes in melt‐quenched glassy models of four different Ge‐Sb‐Te compositions, namely, GeTe, Sb2Te3, GeTe4, and Ge2Sb2Te5. The calculations demonstrate that extra electrons and holes are spontaneously trapped, creating charge‐trapping centers in the bandgap of the amorphous materials. Over‐ and undercoordinated atoms, tetrahedral and “see‐saw” octahedral‐like geometries, fourfold rings, homopolar bonds, near‐linear triatomic configurations, and chain‐like motifs comprise the range of the defective atomic environments that have been identified in the structural patterns of the charge‐trapping sites inside the glassy networks. The results illustrate that charge trapping corresponds to an intrinsic property of the glassy Ge‐Sb‐Te systems, show the impact of electron and hole localization on the atomic bonding of these materials, and they may have important implications related to the operation of phase‐change electronic‐memory devices.