Leakage current in GaN-on-GaN vertical GaN SBDs grown by HVPE on native GaN substrates

This study investigates leakage mechanisms in vertical GaN-on-GaN Schottky barrier diodes (SBDs) and demonstrates effective mitigation strategies. The fabricated devices exhibit low reverse leakage current (1 x 10(-5) A/cm(2) at -200 V) and a high I-on/I-off ratio (similar to 10(10)), surpassing the performance of GaN SBDs on foreign substrates. We elucidate dominant leakage mechanisms-thermionic emission, Poole-Frenkel emission, and variable-range hopping-and their evolution with temperature and bias. Optimized fabrication processes, including defect etching and a novel dual-layer passivation technique, achieve over a 1000-fold reduction in leakage current.