Improving Performances of Enhancement-Mode AlGaN/GaN MIS-HEMTs on 6-inch Si Substrate Utilizing SiON/Al2O3 Stack Dielectrics

Enhancement-mode (E-mode) GaN-based MIS-HEMTs still suffer from undeniable gate leakage or low gate breakdown voltage due to the low quality of gate dielectrics, resulting in a notorious tailing effect of the off-state current. In this letter, a gate scheme featuring SiON/Al2O3 stack dielectrics and partially recessed gate barrier has been employed in the AlGaN/GaN MIS-HEMTs. A high on/off current ratio over $10^{{9}}$ and a small threshold voltage ( ${V} _{\text {th}}$ ) hysteresis less than 20 mV are achieved in the fabricated E-mode devices with a ${V} _{\text {th}}$ around 2.5 V, mainly owing to the reduction of the net positive fixed charge density in the SiON/Al2O3 gate stack confirmed by the ${C}$ - ${V}$ measurements. Meanwhile, a good performance uniformity on 6-inch wafer is achieved which demonstrates the promising scheme for fabricating GaN-based E-mode MIS-HEMT products.