Insight Into Ni/4H-SiC Schottky Barrier Inhomogeneity at Microscale Level

Ni/4H-SiC Schottky barrier diodes (SBDs) are fabricated and then annealed at different annealing temperatures to explore the Schottky barrier inhomogeneity (SBI). The macro-and microelectrical properties of SBDs are characterized by current-voltage (I-V) curves and using a conductive atomic force microscope (CAFM), respectively. The morphologies of the contact surface and the interface are observed using a scanning electron microscope (SEM) and an atomic force microscope (AFM), respectively. The results show that the annealed SBDs exhibit double-barrier characteristics, which come up with two distinct explanations for the observed SBI at different annealing temperatures. The formation of voids in the contact layer and the hexagonal pits in the SiC leads to the SBI in 600 °C-annealed SBDs. As for the 400 °Cand 500 °C-annealed SBDs, only the formation of voids in the contact layer matters. Schottky barriers on the pit (voids) areas are lower (higher) than that on other areas. The established relationship among the annealing temperatures, morphologies, and microelectrical properties deepens the understanding of the barrier inhomogeneity and provides a direction for improving the Schottky barrier homogeneity.