Comparative Investigation of AlGaN/AlN/GaN High Electron Mobility Transistors with Pd/GaN and Pd/Al2O3/GaN Gate Structures

In this article, the electrical characteristics of Al0.28Ga0.72 N/AlN/GaN metal-oxide-semiconductor high electron mobility transistor (MOS-HEMT) with a 20-nm-thick Al2O3 layer by using radio-frequency sputtering as the gate dielectric layer are compared to the conventional metal-semiconductor HEMT (MS-HEMT) with Pd/GaN gate structure. For the insertion of the Al2O3 layer, the energy band near the AlN/GaN heterojunction is lifted slightly up and the 2DEG at the heterojunction is reduced to shift the threshold voltage to the right side. Experimental results exhibits that though the maximum drain current decreases about 6.5%, the maximum transconductance increases of 9%, and the gate leakage current significantly reduces about five orders of magnitude for the MOS-HEMT than the MS-HEMT.