Realizing Giant Ferroelectricity in Stable wz-Al1-xBxN Alloys by Controlling the Microstructure and Elastic Constant

Abstract The emerged wurtzite-type (wz) ferroelectric Al1 − xBxN alloys have drawn increasing attention due to superior ferroelectricity and excellent compatibility with microelectronics. Revealing and controlling the microstructure and ferroelectric origin is vital to design and fabricate stable wz-Al1 − xBxN alloy with giant ferroelectricity. We find that the β-BeO-like rather than h-BN-like structure is the non-polar intermediate phase in the polarization inversion process of stable wz-Al1 − xBxN alloy. The stability and ferroelectric switching pathway of wz-Al1 − xBxN alloy are dominated by the covalent bond strength and elastic constant C₁₄. Due to the reduced internal parameter u and enhanced C₁₄ of wz-Al1 − xBxN alloy, the spontaneous polarization and polarization switching barrier respectively raises and declines as the B concentration increases. Meanwhile, the spontaneous polarization is enlarged by the compression along horizontal direction and tension along c-axis direction, while the polarization switching barrier and band gap are reduced by the all the tension. Moreover, the polarization switching fields are lower than the breakdown fields of wz-Al1 − xBxN alloys with tension. As a result, the giant ferroelectricity with larger spontaneous polarization than wz-Al1 − xScxN alloy and comparable polarization switching barrier to the common ferroelectric oxide is designed in for wz-Al1 − xBxN alloy. It should be noted that the phase transformation concentration of about 0.1875 for wz-Al1 − xBxN alloy is reduced by both tension and compression. These findings give a deeply understanding of ferroelectricity wz-Al1 − xBxN alloy, and provide a guideline to design high-performance ferroelectric wz-Al1 − xBxN alloys.