A Review on Reverse-Bias Leakage Current Transport Mechanisms in Metal/GaN Schottky Diodes

GaN and related nitride semiconductors have attracted considerable interest for use in solid-state light and high-power/-frequency devices. Fabrication of high-quality metal/GaN Schottky contacts is essential to ensure that GaN-based devices perform well. However, GaN Schottky contacts suffer from abnormally high reverse leakage currents that significantly reduce device performance. Hence, a comprehensive understanding of the reverse current transport mechanisms associated with GaN Schottky diodes is essential for reproducible and reliable fabrication of GaN-based devices. In this paper, several possible leakage current transport mechanisms in GaN Schottky devices are briefly reviewed. Poole-Frenkel and thermionic field emissions are generally responsible for the reverse leakage currents of metal/GaN Schottky diodes. In real-world devices, two transport mechanisms can simultaneously contribute to the reverse leakage current, and they must be distinguished to fully understand device performance. In particular, the temperature- and metal electrode-dependent current characteristics require careful and systematic analysis.