Net negative fixed interface charge for Si_3N_4 and SiO_2 grown in situ on 000-1 N-polar GaN

摘要

The electrical properties and trapping characteristics of Si3N4 and SiO2 dielectrics grown in situ on (000-1) N-polar GaN by metal organic chemical vapor deposition are investigated in this paper. The fixed charges, densities of near-interface trap states, and interface trap density in N-polar Si3N4 and SiO2 metal insulator semiconductor capacitors (MISCAPs) are quantified using a capacitance-voltage measurement method which is assisted by ultraviolet illumination and applied voltage-stress. The fixed charges and trap states are located at or near the interface of Si3N4 (SiO2)/N-polar GaN as indicated by the linear relationship between the flatband voltage/hysteresis and the Si3N4 (SiO2) thickness. Positive flatband voltages were measured for both the N-polar Si3N4 and SiO2 MISCAPs which is a promising route toward realizing normally off GaN-based metal insulator semiconductor power devices. Net negative fixed charge densities of 2.9x10(12) cm(-2) and 3.3x10(12) cm(-2) are located at the interface of Si3N4/GaN (N-polar) and SiO2/GaN (N-polar), respectively. The origin of this net negative interface fixed charge is briefly discussed, and the trap densities with fast and slow emission rates are quantified in both the N-polar Si3N4 and SiO2 MISCAPs. This study is a step toward identifying suitable gate dielectrics that can be integrated into N-polar high electron mobility transistors for high-frequency and switching applications.