Interface charge engineering on an <i>in situ</i> SiN<i>x</i>/AlGaN/GaN platform for normally off GaN MIS-HEMTs with improved breakdown performance
Jiaqi He, Kangyao Wen, Peiran Wang, Minghao He, Fangzhou Du, Yang Jiang, Chuying Tang, Nick Tao, Qing Wang, Gang Li, H.Y. Yu
Abstract
This work adopts interface charge engineering to fabricate normally off metal–insulator–semiconductor high electron mobility transistors (MIS-HEMTs) on an in situ SiNx/AlGaN/GaN platform using an in situ O3 treatment performed in the atomic layer deposition system. The combination of in situ SiNx passivation and an O3-treated Al2O3/AlGaN gate interface allows the device to provide an excellent breakdown voltage of 1498 V at a low specific on-resistance of 2.02 mΩ cm2. The threshold voltage is increased by 2 V by significantly compensating the net polarization charges by more than five times with O3 treatment as well as reducing the interface traps and improving the high-temperature gate stability. Furthermore, a physical model of fixed charges at the Al2O3/AlGaN interface is established based on dielectric thickness-dependent linear fitting and numerical calculations. The matched device performance and simulated energy band bending elucidate the O3-treated fixed-charge modulation mechanism, providing a practical method for producing normally off GaN MIS-HEMTs.