In this study, intrinsic Ga2O3 (i-Ga2O3) film was deposited at about 80 K using a vapor cooling condensation system. Its bandgap energy was 5.0 eV. Low oxygen vacancy and defects were verified by using photoluminescence and Hall measurements. When a 40-nm-thick i-Ga2O3 film was used as the gate dielectric layer of AlGaN/GaN metal-oxide-semiconductor high-electron mobility transistors (MOS-HEMTs), threshold voltage, and gate breakdown voltage were − 3.5 V and − 538.0 V, respectively. The associated gate leakage current of the devices operating at a gate-source voltage of − 100 V was 0.57 μA. Furthermore, a saturation drain-source current of 186.2 mA/mm and a maximum extrinsic transconductance of 85.8 mS/mm were obtained for the devices operating at a gate-source voltage of 0 V and a drain-source voltage of 10 V. The unit gain cutoff frequency and the maximum oscillation frequency were 5.7 GHz and 11.0 GHz, respectively. The normalized noise and Hooge’s coefficient were 3.79 × 10−14 Hz−1 and 5.06 × 10−5, respectively, when the devices operated at a frequency of 100 Hz, with a drain-source voltage of 1 V and a gate-source voltage of 5 V.
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