Effects of Y Dopant on Lattice Distortion and Electrical Properties of In₃SbTe₂ Phase‐Change Material

Abstract

Using a computational high‐throughput screening method, 29 doping elements have been investigated for improving the thermal and electrical characteristics of In3SbTe2 (IST) phase‐change material. Among the 29 dopants, it is found that Y offers largest distortion in the lattice structure of IST with negative doping formation energy while Y substitutes the In site. The atomic lattice images clearly show that the In site is substituted by Y and the distortion angles of the Y‐doped IST (Y‐IST) are well matched with the calculated results of density functional theory (DFT). Set/reset speed of the Y‐IST phase‐change memory is faster than IST and Ge2Sb2Te5 (GST) devices, which is strongly related with the fast and stable phase transition due to the larger lattice distortion. The power consumption of the Y‐IST device is also less than a fourth of that of the GST device.

Interface-Driven Phase Transition of Phase-Change Material

“…The models of InSb/a-Bi and InTe/a-Bi consist of In 32 Sb 32 Bi 64 and In 20 Te 20 Bi 35 , respectively. In our previous work, 26 the effect of the change in system size on the energy parameters such as doping formation energy was verified; moreover, the reliability of a 2 × 2 × 2 supercell (64 atoms) of IST for doping modeling was tested via a comparison with a 3 × 3 × 3 one (216 atoms). 26,59 The energy difference was less than 0.1 eV.…”

“…In our previous works, it was observed that the set and reset switching speeds of PCRAMs fabricated using IST doped with Y and Bi elements (Y 12.38 (In 3 SbTe 2 ) 87.62 and Bi 5.5 (In 3 SbTe 2 ) 94.5 ) are evidently more effective than those of the devices fabricated with pure IST and GST. Such an improvement is strongly related to the effects of lattice distortion in the doped IST.…”

“…9−17 Thus, a doping method has been recommended to solve these problems related with metastable phase change and to improve the characteristics of PCMs, such as endurance, retention, switching speed, and operation voltage. A number of dopants (for example, Sn, 18 Ti, 19 Bi, 20 Zn, 21,22 W, 23 In, 24 Cr, 25 and Y 26 ) have been studied with GST and IST PCMs; moreover, electrical characteristics are investigated together with the crystal structure, chemical bonding, shift of phase transition temperatures, etc.…”

“…Moreover, the metastable crystalline phase causes severe problems related to phase stability, such as phase separation and element segregation during repeated switching operations; these finally result in resistance drift and data error. − Thus, a doping method has been recommended to solve these problems related with metastable phase change and to improve the characteristics of PCMs, such as endurance, retention, switching speed, and operation voltage. A number of dopants (for example, Sn, Ti, Bi, Zn, , W, In, Cr, and Y) have been studied with GST and IST PCMs; moreover, electrical characteristics are investigated together with the crystal structure, chemical bonding, shift of phase transition temperatures, etc.…”

“…In addition, the phase transition of second intermediate phases to stable crystalline IST will be analyzed in conjunction with the interfacial energy, the difference in the bulk free energies between the second intermediate phases and the stable crystalline IST, as well as the interfacial energy of the element. Although the interfacial energy is frequently discussed in conjunction with the heterogeneous crystal nucleation, ,, the phase transition processes in IST and Bi-IST have not been thoroughly explained in terms of the energy barrier, interfacial energy, and bulk energy. ,− Furthermore, it will be highly effective to implement a noble PCM by regulating the stable phase transition for various applications such as a three-dimensional (3D) X-point memory and synaptic application. − …”