SiO₂/β-Ga₂O₃ (001) MIS Capacitors With Ideal Flat Band Voltage, Small Hysteresis, and Low Interface Traps

In this study, we have fabricated a high-performance SiO2/beta gallium oxide ( $\beta $ -Ga2O3) (001) metal-insulator–semiconductor (MIS) capacitor. Its high-temperature thermal stability was investigated in detail. No significant frequency dispersion was observed by the bidirectional frequency-dependent C–V characteristics. The SiO2/ $\beta $ -Ga2O3 (001) MIS capacitor with postdeposition annealing (PDA) at 1000 °C demonstrates an ideal flat band voltage ( ${V}_{\text {FB}}$ ) of 1.0 V, low flat band hysteresis voltage of 40 mV, as well as low interface state density ( ${D}_{\text {it}}$ ) of below $5\times 10^{{11}}$ cm−2 eV−1. However, for the sample annealed at 1100 °C, the ${V}_{\text {FB}}$ increased to 2.1 V, indicating a high density of fixed charge in SiO2 film. The gate leakage current density remains below $1\times 10^{-{6}}$ A/cm−2 for 1000 °C-annealed SiO2/ $\beta $ -Ga2O3 (001) MIS capacitor until hard breakdown occurs. The ${D}_{\text {it}}$ values of SiO2/ $\beta $ -Ga2O3 (001) interfaces with PDA at 800 °C, 900 °C, and 1000 °C are lower than $5\times 10^{{11}}$ cm−2 eV−1 within the trap energy level range of $0.2\le {E}_{C}-{E}_{t} \le 0.6$ eV. However, the sample after annealing at 1100 °C, the ${D}_{\text {it}}$ values are higher than that of the other three capacitors. High-angle annular dark field scanning transmission electron microscope (HAADF-STEM) was performed to investigate interface characteristics of the SiO2/ $\beta $ -Ga2O3 (001) MIS capacitor with PDA at 1100 °C. The depth profiles of Ga and Si in SiO2 films and at the surface of $\beta $ -Ga2O3 after PDA at 1000 °C and 1100 °C were measured by dynamic secondary ion mass spectrometry measurements. These results indicate the formation of high-quality SiO2 film on the (001) oriented $\beta $ -Ga2O3 after high-temperature annealing, making it a potential candidate as gate dielectrics in $\beta $ -Ga2O3 power devices.