Abstract: In this paper, the Ga₂O₃ field-effect transistors were fabricated on the Ga₂O₃ epitaxial material grown by MOCVD, and their performances were studied. In order to reduce the on-resistances of the transistors, the epitaxial layer was optimally designed and the doping concentration was increased to above 1×10¹⁸ cm^-3. The electron concentration and field-effect mobility of the epitaxial layer extracted from the long channel transistor were 2×10¹⁸ cm^-3 and 55 cm²/(V·s), respectively, which result in a corresponding channel sheet resistance of 10.3 kΩ/sq. The specific on-resistances of the Ga₂O₃ MOSFETs with gate to drain spacings of 2 and 16 μm were 2.3 and 40.0 mΩ·cm², and the corresponding breakdown voltages were 458 and 2 324 V, respectively. In order to further improve the breakdown voltages of the transistors, the p-type NiO gates were employed. The on-resistances of the fabricated Ga₂O₃ JFETs were significantly increased, but the breakdown voltages were improved to 755 V and above 3 000 V, respectively. The power figure of merits (P-FOMs) of the transistors with different gate to drain spacings were calculated, and it was found that they increased first and then decreased with the increase of the gate to drain spacings. The Ga₂O₃ MOSFET with a gate to drain spacing of 8 μm achieved the highest P-FOM, which was 192 MW/cm², indicating the MOCVD epitaxial technology demonstrates an important application prospect for Ga₂O₃ power transistors.

Key words: gallium oxide, MOCVD epitaxial, doping, specific on-resistance, breakdown voltage, power figure of merit