Transport and Breakdown Mechanisms of Gate Leakage Current in Lattice-Matched In₀.₁₇Al₀.₈₃N/GaN HEMTs

Charge transport and breakdown mecha- nisms of gate leakage current in lattice-matched In0.17Al0.83N/GaN high electron mobility transistors (HEMTs) were investigated by combining the current–voltage (
${I}-{V}$
) measurement, the bias-step stress method, and the emission microscopy (EMMI) technique. Based on a refined dislocation model, the detailed dislocation-related charge transport processes were depicted, suggesting an excessive Fowler–Nordheim (FN) tunneling current at high reverse biases. It is further proposed that: 1) at the heterojunction interface, these tunneling electrons will lose the obtained energy by releasing a large number of photons as “hot spots” and phonons as heat and 2) due to a reduced effective bandgap, the breakdown electric field at the dislocation site is significantly decreased compared with the defect-free region, which triggers a premature current breakdown, once the surface electric field is increased to the critical value.