Electrical breakdown strength enhancement in aluminum scandium nitride through a compositionally modulated periodic multilayer structure

In this study, we report the effects of a multilayer architecture on the electrical breakdown strengths and ferroelectric characteristics of 45 nm thick aluminum scandium nitride (AlScN) films. Multilayered films (three-layer, five-layer, and seven-layer) are deposited via sequential deposition of Al0.72Sc0.28N and Al0.64Sc0.36N while maintaining constant volume ratios in all three samples. The effect of the increased number of interfaces is compared to 45 nm single layer Al0.72Sc0.28N and single layer Al0.64Sc0.36N films. The Weibull analysis shows an increase in the characteristic breakdown field from 5.99 and 5.86 MV/cm for single layer Al0.72Sc0.28N and Al0.64Sc0.36N to as high as 7.20 MV/cm in the seven-layered sample. The breakdown field to coercive field (EBD/Ec) ratios also increase from 1.37 and 1.26 in single layer Al0.72Sc0.28N and Al0.64Sc0.36N to up to 1.44 in the seven-layered sample with no significant change in remanent polarization. The enhancement of the characteristic breakdown field can be understood as the propagation of the electrical tree being deflected by multilayer interfaces and/or being slowed by the relative compressive stress in the alternating layers.