Yttrium-Doped Sb₂Te₃: A Promising Material for Phase-Change Memory

Abstract

Sb₂Te₃ exhibits outstanding performance among the candidate materials for phase-change memory; nevertheless, its low electrical resistivity and thermal stability hinder its practical application. Hence, numerous studies have been carried out to search suitable dopants to improve the performance; however, the explored dopants always cause phase separation and thus drastically reduce the reliability of phase-change memory. In this work, on the basis of ab initio calculations, we have identified yttrium (Y) as an optimal dopant for Sb₂Te₃, which overcomes the phase separation problem and significantly increases the resistivity of crystalline state by at least double that of Sb₂Te₃. The good phase stability of crystalline Y-doped Sb₂Te₃ (YST) is attributed to the same crystal structure between Y₂Te₃ and Sb₂Te₃ as well as their tiny lattice mismatch of only ∼1.1%. The significant increase in resistivity of c-YST is understood by our findings that Y can dramatically increase the carrier's effective mass by regulating the band structure and can also reduce the intrinsic carrier density by suppressing the formation of Sb_Te antisite defects. Y doping can also improve the thermal stability of amorphous YST based on our ab initio molecular dynamics simulations, which is attributed to the stronger interactions between Y and Te than that of Sb and Te.