GOX 2023 Session DI-MoP: Dielectric Interfaces Poster Session I

We report on the growth and characterization of in-situ Al₂O₃ on (010) β-Ga₂O₃ deposited using metalorganic chemical vapor deposition (MOCVD) to enhance the dielectric quality and lifetime. The growth of Al₂O₃ is performed after the growth of β-Ga₂O₃ without breaking the vacuum in an Agnitron MOVPE reactor using Trimethylaluminum (TMAl) and Oxygen as precursor gas. The interfacial dielectric layer (First 5nm) is grown at 800 °C to crystallize the interface to have reduced interface trap density and the rest of the dielectric (17nm) is grown at 600 °C. Grazing incident Xray diffraction analysis was performed, and polycrystalline inclusions were observed in the grown Al₂O₃ films. The dielectrics grown at 600 °C exhibited higher interface trap density (D_t=3.2×10¹² cm^-2) and lower breakdown field (E_BR=6MV/cm) compared to the dielectric grown at 800 °C (E_BR=10MV/cm,D_t=5.4×10¹¹ cm^-2) characterized using deep-UV assisted CV measurements and the current-voltage characteristics of the MOS capacitors. The temperature-modulated dielectric sample (interfacial layer grown at 800 °C, and the bulk dielectric grown at 600 °C) has higher breakdown strength (E_BR=7.7MV/cm) and lower trap density (D_t=1.1×10¹² cm^-2) compared to the dielectric grown at 600 °C. This is possibly due to the interfacial crystallization of the hybrid dielectric due to the initial growth at higher temperature. Time dependent dielectric breakdown (TDDB) was also performed to characterize the long-term reliability of the grown dielectrics. From the Weibull distribution plots of the time to breakdown for four different TDDB stress condition, shape factor β>1 was extracted indicating good statistical uniformity and intrinsic breakdown behavior. The TDDB distribution is much tighter (higher β value) for the 600 °C dielectric, compared to the 800 °C grown dielectric. This is possibly due to the short-range ordering of the 800 °C dielectric compared to the 600 °C dielectric, which reduces the long-term reliability of the dielectric. However, for the hybrid dielectric, the time to breakdown is found to be much tightly distributed compared to both 600 °C & 800 °C dielectric. Based on the E-model, the lifetime of the 800 °C can be extended to 10 years if the dielectrics are stressed at 0.7MV/cm, whereas the hybrid dielectric can be stressed at 3.1MV/cm to have 10 years of lifetime. Thus although the static breakdown voltage and trap densities of the hybrid dielectric are a little inferior compared to the 800 °C dielectric, the long term reliability of the hybrid dielectric is much superior.