Incongruent melting phenomenon shows the feasibility of multilevel control using the phase‐change material Ga2Te3Sb5 (Ga‐TS). Electrical results showed that Ga‐TS cells require 25% less RESET current than do GST cells. Meanwhile it possesses a high programming speed, ultralong data retention extrapolated to one million years at 120 °C, and superior thermal properties for phase‐change random‐access‐memory applications.

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Phase change memory (PCM) cells with T-shaped structure using tungsten heater were fabricated and the cell characteristics concerning the programing pulse width were also investigated in this work. The numerical modeling shows the thermal nonuniformity over the active region due to the considerable thermal sink of tungsten heater results in the amorphous-phase residues and the incomplete set programing. The experimental results reveal the existence of residual amorphous phase and indicate that the incomplete set programing is the dominant factor to degrade the PCM cell performances, such as the sensing margin and the endurance. The strategies to eliminate the incomplete set programing are the optimization in programing pulse width and the replacement of the tungsten heater with higher resistivity metal such as TiAlN.

Mechanical properties of as-deposited GeSbTe media on SiO 2 /Si(100) with different compositions and film thicknesses were successfully investigated by using the microcantilever method and nanoindentation. All the studied films show a compressive residual stress state, which increases proportionally to the elastic constant. Because of the accumulating effects during film deposition, the mechanical properties of these GeSbTe films can be greatly affected. As the film thicknesses were 20 and 25 nm, compared with the Ge 4 SbTe 5 and Ge 4 Sb 0.5 Te 5 Bi 0.5 films, the Ge 2 Sb 2 Te 5 film has the highest residual stress value ranging from 3 MPa to 15 MPa. When the film thickness was 30 nm, the composition-induced stress relaxation occurred. Bi addition, which leads to lattice expansion in Ge 4 SbTe 5 films, resulted in a decrease of stress. Compared with the Ge 4 SbTe 5 and Ge 4 Sb 0.5 Te 5 Bi 0.5 films, the Ge 2 Sb 2 Te 5 film also has the lowest coefficient of thermal expansion (CTE) value ranging from 2×10 −6 to 7×10 −6 / • C, and a lower CTE was obtained when the film thickness was increased. By nanoindentation, the Ge 4 SbTe 5 film shows higher hardness and elastic constant than those of the Ge 2 Sb 2 Te 5 film. The measured hardnesses for Ge 2 Sb 2 Te 5 and Ge 4 SbTe 5 films are 12 GPa and 18 GPa; and the reduced elastic modului are 120 GPa and 140 GPa, respectively.

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