Analysis of leakage current mechanisms in AlInGaN/GaN metal-insulator-semiconductor capacitors

For emerging 5G millimeter-wave base stations and automotive radar systems operating in the V/W bands, suppressing gate leakage currents in AlInGaN/GaN MIS capacitors is critical to mitigate energy losses exceeding 15 % and thermal runaway risks under high-power RF conditions. This study systematically investigates the leakage mechanisms in AlInGaN/GaN Metal-Insulator-Semiconductor (MIS) capacitors, focusing on the influence of electrode geometry. We analyze the factors governing leakage behavior by fabricating devices with a series of electrode dimensions and spacings, and conducting comprehensive current–voltage (I-V) and capacitance–voltage (C-V) measurements. The results demonstrate that reducing electrode spacing intensifies local electric field concentration, enhancing trap-assisted tunneling at the interface and thereby increasing leakage current density. Conversely, increasing electrode size and spacing improves the uniformity of the electric field distribution and significantly mitigates the leakage currents. In addition, C-V measurement shows that the Si₃N₄ passivation process can effectively suppress the defects of the heterojunction interface. After passivation, the interface state density decreases to 6.1 × 10¹¹ cm⁻² eV⁻¹. Further analysis elucidates the voltage-dependent nature of leakage mechanisms: ohmic conduction dominates in low-field regions, while Schottky emission and Frenkel-Poole emission contribute in medium-to-high fields, with Fowler-Nordheim tunneling prevails under high electric fields. These findings emphasize the critical role of optimizing electrode geometries and interface passivation strategies in enhancing device reliability. This work provides theoretical insights and experimental guidance for advancing high-frequency, high-power GaN-based devices for emerging applications in communications and RF technologies.