Effect of Atomic Layer Deposited AlN Layer on Pt/4H-SiC Schottky Diodes

Thin AlN layer was deposited on n-type 4H-SiC using atomic layer deposition and the electrical properties of Pt/SiC Schottky diodes with and without AlN layer were comparatively investigated. Based on the capacitance–voltage (C–V) and conductance–voltage (G/ω–V) characteristics, the interface state density decreased but the oxide trap density increased with an AlN layer. The border traps present near the AlN/SiC interface might produce such difference. Compared to the sample without AlN, both the barrier height and the ideality factor increased with an AlN. Analyses on the reverse leakage current density for Pt/AlN/SiC junction showed that the dominant transport mechanisms are ohmic conduction, trap assisted tunneling (TAT) and Fowler–Nordheim emissions at low, intermediate, and high electric field regions, respectively. Both the nitrogen vacancies and dangling bonds in Al in AlN layer were suggested to contribute to the TAT conduction.