High Contact Resistivity Enabling Low‐Energy Operation in Cr₂Ge₂Te₆‐Based Phase‐Change Random Access Memory

A phase‐change material (PCM) exhibiting a significant difference in resistance between the amorphous and crystalline phases can be used for phase‐change random access memory (PCRAM). Reduction of the energy to operate is one of the major challenges in PCRAM technology. One strategy for energy reduction is to increase the resistance of the memory device in the crystalline state of the PCM. Cr₂Ge₂Te₆ (CrGT) shows p‐type semiconductor characteristics in both the amorphous and crystalline phases. A CrGT‐based memory device shows a contact resistance–dominant behavior, suggesting that the resistance of a CrGT‐based memory device can be increased by changing the electrode material. The contact resistivity (ρ_c) of a CrGT/electrode increases with a decrease in the work function of the electrode material in both amorphous and crystalline phases, as with general p‐type semiconductor materials. The highest ρ_c is observed for a LaB₆ electrode. The resistance of the CrGT‐based device with a LaB₆ electrode (LaB₆ device) is three or four orders of magnitude greater than that of a device with a W electrode (W device). The LaB₆ device is indicated to require much smaller operation energy than the W device.