Ferroelectric epitaxial Al(Sc/B)N/Mo/SiC heterostructures for high operating temperature devices

Advances in wurtzite nitride ferroelectrics of Al1−xMxN (M = Sc or B) have led to novel capabilities, which must be integrated into existing fabrication processes. In the case of electronics operating >200°C, a movement toward SiC-based platforms enables better performance over conventional Si, primarily due to the higher bandgap and lower intrinsic carrier concentration of SiC. Hence, the challenge is to develop a deposition process to integrate Al1−xMxN ferroelectrics with elevated temperature-compatible materials for high temperature electronics such as the non-volatile memory component. We demonstrate epitaxial AlMN/Mo/SiC heterostructures, which provides both the crystalline and surface features that promote high-quality ferroelectric nitride film growth. Omega scans of the Mo (110) reflection exhibit a full width at half max of <0.02° (40 arc sec) and the (0002) peak of the subsequently grown nitride film had a value of 1.1° for 160 nm thick Al0.7Sc0.3N and 1.3° for 400 nm thick Al0.94B0.06N. The crystallographic relationships found between the AlMN, Mo, and SiC layers indicate an advancement in sputter deposition of epitaxial films. Ferroelectric switching is also shown at 400 °C in both samples via polarization-electric field hysteresis and pulsed measurements, which exhibited Pr values >100 μC cm−2 and Ec between 3 and 4 MV cm−1, despite a large presence of oxygen in both AlMN films ranging between 4 and 5 at.%, revealed by compositional analysis. This study demonstrates the process for synthesizing high-crystal quality ferroelectric nitride films, which can be used in extremely high temperature applications.