Ionic Transport Barrier Tuning by Composition in Pr1–xCaxMnO3-Based Selector-Less RRAM and Its Effect on Memory Performance

Selector-less resistive random-access memory (RRAM) devices require high nonlinearity (NL) in low resistance state current (ILRS). In this paper, we investigate the effect of composition (here, Ca%)-dependent material properties, viz., ion migration barrier, and thermal conductivity, on memory performance of recently demonstrated Pr
_1-x
Ca
_x
MnO
₃
-based selector-less RRAM with high NL. First, the NL increases as “x” decreases. This is attributed to higher self-heating in PCMO(x) films as composition dependent thermal conductivity (κ) decreases as “x” is decreased. This enables selector-less operation. Second, larger memory window is observed as “x” increases due to decrease in the voltage required for onset of RESET process (i.e., VMIN, RESET) as “x” is increased. Lower VMIN, RESET at higher “x” is due to higher oxygen-ion conductivity attributed to lower migration barrier (Em). Third, retention is measured at different temperatures to extract composition dependent Em. The poor memory retention performance for x = 1 is consistent with lower Em estimated. Finally, enhanced endurance is observed for lower Em due to low energy requirement for switching. Based on these observations, an interrelation between Em, retention, and endurance is established. Therefore, an interplay of composition dependent thermal conductivity and oxygen-ion migration barrier enables tunable memory characteristics in Pr
_1-x
Ca
_x
MnO
₃
-based RRAM.