Surface Acceptor-Like Trap Model for Gate Leakage Current Degradation in Lattice-Matched InAlN/GaN HEMTs

Typical leakage current degradation behaviors are observed in lattice-matched In0.17Al0.83N/GaN Schottky structure, suggesting that the inverse piezoelectric effect may not be the major mechanism causing gate degradation in the stress-free GaN HEMTs. The low-field current is dominated by Poole-Frenkel emission of electrons with the compensation effect, indicative of the presence of deep-level acceptor-like traps in the surface barrier layer. A new surface acceptor-like trap model is developed to address the degradation kinetics, emphasizing that the high-field Fowler-Nordheim tunneling process may cause the generation of the acceptor-like defects, which could in turn introduce a thinner surface barrier to enhance the tunneling component, and the corresponding threshold voltage should determine the critical voltage of gate degradation.