Effect of doping on the ferroelectric properties of wurtzite Al1 <b>−</b> xYxN

Abstract

Ferroelectric materials can be used to fabricate ferroelectric random-access memory with significant performance advantages. Recently, doped wurtzite-type ferroelectrics have attracted widespread attention. We use first-principles calculations to investigate the structural, electronic, and ferroelectric properties of Y-doped AlN (Al1−xYxN). Our results reveal that the Y-doped AlN exhibits a large spontaneous polarization comparable to that of the Sc-doped AlN, and a relatively low ferroelectric switching barrier. Furthermore, its lower material cost and wider wurtzite phase concentration range make it more practical than Sc-doped AlN. This study further reveals that the high energy barrier hindering polarization reversal originates from the covalent Al-N bonds with high bonding strength. The calculated results indicated that the ferroelectric switching barrier decreases progressively with increasing doping concentration. This is attributed to the formation of weaker chemical bonds due to the addition of the rare-earth metal element Y, making the system more ionic and thus facilitating polarization reversal. Our work expands the ferroelectric family of the wurtzite III-nitrides and provides a physical mechanism for the reduction of energy barriers through doping, which holds significant guiding value.