Abstract
In this study, we investigated the performance of gallium nitride (GaN) enhancement mode n-channel metal-oxide-semiconductor field effect transistor (n-MOSFET) with different gate dielectrics. It is very difficult to obtain a good interface, low leakage current and high κ value for only one single dielectric layer on GaN substrate. In order to improve electrical properties and demonstrate good quality of high κ gate dielectric stacks on p-type GaN, we use several surface passivation on several multi-layer nano-scaled dielectrics. Aluminum oxide (Al2O3), magnesium oxide (MgO) and titanium oxide (TiO2) were combined in these nanolaminate structures in this study, and an enhancement mode GaN n-type channel MOSFET was demonstrated successfully. The leakage current of the stacked MgO (5 nm) and hybrid MgO-TiO2 (1:1, 10 nm) MOS capacitor can be as low as 6.2 × 10-9 and 6.9 × 10-9 A/cm2 under ± 1 V bias, respectively. By means of a self-aligned process, a MOSFET with excellent ID-VD and ID-VG electrical characteristics was obtained. At the gate voltage VG of 8 V and the drain voltage VD of 10 V, the maximum drain current is 36.9 mA/mm. The subthreshold swing is 342 mV/dec and the Ion/Ioff ratio is 5.7 × 104.