Comparative studies of AlGaN/GaN MOS-HEMTs with stacked gate dielectrics by the mixed thin film growth method

This paper reports Al_0.27Ga_0.73N/GaN metal-oxide-semiconductor high electron mobility transistors (MOS-HEMTs) with stacked Al₂O₃/HfO₂ gate dielectrics by using hydrogen peroxideoxidation/sputtering techniques. The Al₂O ₃ employed as a gate dielectric and surface passivation layer effectively suppresses the gate leakage current, improves RF drain current collapse and exhibits good thermal stability. Moreover, by stacking the good insulating high-k HfO₂ dielectric further suppresses the gate leakage, enhances the dielectric breakdown field and power-added efficiency, and decreases the equivalent oxide thickness. The present MOS-HEMT design has demonstrated superior improvements of 10.1% (16.4%) in the maximum drain-source current (I_DS,max), 11.4% (22.5%) in the gate voltage swing and 12.5%/14.4% (21.9%/22.3%) in the two-terminal gate-drain breakdown/turn-on voltages (BV_GD/V_ON), and the present design also demonstrates the lowest gate leakage current and best thermal stability characteristics as compared to two reference MOS-HEMTs with a single Al ₂O₃/(HfO₂) dielectric layer of the same physical thickness.