Effects of nitrogen passivation on the capture cross section energy distribution of 4H-SiC/SiO2 interface defects and the temperature dependences of leakage current

Abstract

Nitrogen passivation has been established as an effective method to decrease the interface state density (Dit) for silicon carbide (SiC) devices. However, the effect of nitrogen passivation on the carrier capture cross section distributions of SiC/SiO2 interface defects is still unclear, which is another critical factor governing the interface recombination characteristics and device performances of SiC power devices. In this work, the local band bending is regulated in deep level transient spectroscopy characterizations to modulate the carrier capture and emission behaviors of interface defects in localized energy levels. Therefore, the distribution of carrier capture cross section is determined as a function of the interface state density. Surprisingly, it is found that nitrogen passivation leads to an increase in the capture cross sections of SiC/SiO2 interface defects, especially for deeper interface states within the bandgap. Based on those findings, the mechanisms of the temperature dependence of leakage current characteristics are explored, where the leakage currents first decrease with rising temperature, reaching a minimum at 250 K, and subsequently increase further with elevated temperature. An interfacial defect-assisted Fowler–Nordheim tunneling mechanism is proposed to explain the temperature dependence of leakage currents, which is suggested to originate from the synergistic interplay between the energy-level dependent capture cross section and interface state densities.