Influence Mechanism of Barium Interface Layer on the Interfacial Properties of n‐Type 4H‐SiC Metal–Oxide–Semiconductor Capacitors.

The 4H‐SiC/SiO2 interface quality can be significantly improved by adding an alkaline earth metal interface layer. To study the passivation mechanism of the alkaline earth metal barium (Ba), a supercell model with a transition layer is established. As shown in the results from first‐principles calculations, the bandgap increases and the density of states decreases when SiBaO or OBaO structures are introduced into the transition layer. 4H‐SiC/Ba interface layer/SiO2 capacitors with different annealing conditions are fabricated. X‐ray photoelectron spectroscopy results show that Ba mainly exists in the form of BaO2 (corresponding to the OBaO structure) after annealing in 5% O2 in Ar atmosphere, and there are fewer types of suboxides in the interface than those annealed in Ar. A small amount of Ba also combines with SiO2 to form SiBaxOy compounds (corresponding to the SiBaO structure). The correctness of the theoretical analysis is verified by capacitance–voltage measurements. The physical mechanism of Ba passivation is analyzed in this article, which helps to improve the performance of SiC metal–oxide–semiconductor (MOS) structure devices. [ABSTRACT FROM AUTHOR]