Effect of Barrier Layer Thickness on Gate Leakage Current in AlGaN/GaN HEMTs

Gate leakage current mechanisms in Al_0.28Ga_0.72N/GaN high-electron mobility transistors with different barrier thicknesses are studied using temperature-dependent current-voltage characteristics. Poole-Frenkel emission and Fowler-Nordheim tunneling are observed in the reverse bias. Beyond the threshold voltage, increase in gate leakage current with the increase in barrier thickness is observed. Furthermore, the gate leakage current has negative temperature dependence over a wide range of temperatures especially for the devices with a thicker barrier. This has been qualitatively explained with the help of secondary electron-hole pair generation in the channel.