Barrier inhomogeneity and leakage current transport mechanism in vertical Pt/Gd₂O₃/GaN Schottky diodes

Vertical Pt Schottky contacts to bulk GaN single crystal with an ultrathin Gd₂O₃ interlayer grown by atomic layer deposition were electrically characterized using temperature dependent current–voltage (I–V–T) and capacitance–voltage (C–V) measurements. The forward I–V characteristics of the Schottky diodes revealed a temperature dependence of barrier height, and were explained by thermionic emission involving barrier inhomogeneity. Based on the thermally activated process, the dominant transport mechanism for reverse leakage current was determined to be Poole–Frenkel emission with the trap energy of 0.78 eV. The flat-band barrier height estimated from C–V method was 1.33 eV. The analysis on C–V data showed very low interface state density, indicating that Gd₂O₃ is a promising passivation layer in vertical GaN devices.