Role of Defects in the Breakdown Phenomenon of Al1-x Sc x N: From Ferroelectric to Filamentary Resistive Switching

Aluminum scandium nitride (Al1-x Sc x N), with its large remanentpolarization,is an attractive material for high-density ferroelectric random-accessmemories. However, the cycling endurance of Al1-x Sc x N ferroelectric capacitorsis far below what can be achieved in other ferroelectric materials.Understanding the nature and dynamics of the breakdown mechanism isof the utmost importance for improving memory reliability. The breakdownphenomenon in ferroelectric Al1-x Sc x N is proposed to be an impulse thermalfilamentary-driven process along preferential defective pathways.For the first time, stable and robust bipolar filamentary resistiveswitching in ferroelectric Al1-x Sc x N is reported. A hot atom damage defectgeneration model illustrates how filament formation and ferroelectricswitching are connected. The model reveals the tendency of the ferroelectricwurtzite-type Al1-x Sc x N system to reach internal symmetry with bipolarelectric field cycling. Defects generated from bipolar electric fieldcycling influence both the energy barrier between the polarizationstates and that required for the filament formation.