Interface charge engineering on an in situ SiN_x/AlGaN/GaN platform for normally off GaN MIS-HEMTs with improved breakdown performance

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 O-3 treatment performed in the atomic layer deposition system. The combination of in situ SiNx passivation and an O-3-treated Al2O3/AlGaN gate interface allows the device to provide an excellent breakdown voltage of 1498 V at a low specific on-resistance of 2.02m Omega cm(2). The threshold voltage is increased by 2V by significantly compensating the net polarization charges by more than five times with O-3 treatment as well as reducing the interface traps and improving the hightemperature 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 O-3-treated fixed-charge modulation mechanism, providing a practical method for producing normally off GaN MIS-HEMTs.