Ferroelectric Epitaxial Al(Sc/B)N/Mo/SiC Heterostructures For High Operating Temperature Devices: Article No. 204102

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 degrees 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 Al MN/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 degrees (40 arc sec) and the (0002) peak of the subsequently grown nitride film had a value of 1.1 degrees for 160 nm thick Al0.7Sc0.3N and 1.3 degrees 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 degrees C in both samples via polarization-electric field hysteresis and pulsed measurements, which exhibited Pr values >100 ..mu..C cm-2 and Ec between 3 and 4 MV cm-1, despite a large presence of oxygen in both Al MN 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.