Design strategy of phase change material properties for low-energy memory application

Understanding the Origin of Low-Energy Operation Characteristics for Cr2Ge2Te6 Phase-Change Material: Enhancement of Thermal Efficiency in the High-Scaled Memory Device

“…Recently, we established a new simulation scheme that simultaneously solves the electrical potential and temperature distribution, even in the case of the application of pulse voltage . We have already demonstrated that this scheme is effective in revealing the correlation between operation energy and material properties by combining with machine learning …”

“…At the top and bottom boundaries, the electrical potential was set to ϕ h and 0 V, respectively, and the temperature at both side boundaries was set to 298 K. The heat flux at the material interface was balanced as follows where n is the unit normal vector to the boundary and the subscripts a and b indicate the adjacent materials. At the material interface, except for the TiN/PCM interface, the current flow is balanced as At the TiN/PCM interface, the contact resistance was considered as where Δϕ i is the contact electrical potential and ρ C ′ is the pseudo-contact resistivity. , The latter is an important parameter for incorporating the interfacial properties into the numerical simulation. In the case of GST, ρ C ′ is constant because of the Ohmic I – V characteristics.…”

“…In a previous study, our research group reported that the operation energy E can be simplified as follows where C is a constant expressing the degree of contact resistance dominance, Δ T is the temperature increase, and Δ z is the thickness of PCM, which is equivalent to t . As t increases, C should be lowered; however, the bulk σ increases because the percolation effect increases C .…”

“…Cr 2 Ge 2 Te 6 (CrGT) is an inverse resistance change-type PCM that shows high-resistive crystalline and low-resistive amorphous phases. , Because of the small ratio of contact resistivity to bulk resistivity of crystalline CrGT, the operation energy for amorphization is quite low in CrGT-based devices . In addition, unlike conventional PCMs, the operation energy for crystallization dominates for total operation energy in CrGT-based devices .…”

“…36,37 Meanwhile, in most cases using conventional calculation schemes, the forcible application of current is considered to reproduce a sufficiently large Joule heat, 36,37 38 We have already demonstrated that this scheme is effective in revealing the correlation between operation energy and material properties by combining with machine learning. 17 To evaluate the effect of the physical properties of PCMs on operation energy, the balance equations of heat and electrical potential were solved. These governing equations were the same as those used in the previous study 38…”