Fig. 1. (Color online) (a) Cross-sectional schematic and (b) current density−voltage curves of the MOS device on the p⁺⁺-GaN/p-GaN/AlN/AlGaN/AlN/GaN heterostructure.

Fig. 2. (Color online) (a) Cross-sectional schematic of the fabricate E-mode GaN p-FETs. (b) TLM analysis of the ohmic contact. (c) Benchmarking the R_c and hole sheet density of the fabricated GaN p-FET with some state-of-the-art GaN p-FETs. (d) Depth profile of the gate recess trench measured by the atomic force microscope. The inset figure presents measured resistances as a function of ohmic metal spacing.

Fig. 3. (Color online) (a) DC transfer and (b) SS vs I_D plot of fabricated GaN p-FETs with the O₃-Al₂O₃ and O₃-Al₂O₃/HfO₂ stack as the gate dielectric.

Fig. 4. (Color online) (a) DC output and (b) OFF-state characteristics of fabricated GaN p-FETs with the O₃-Al₂O₃ and O₃-Al₂O₃/HfO₂ stack as the gate dielectric.

Fig. 5. (Color online) (a) Output characteristics for the GaN p-FET using O₃-Al₂O₃/HfO₂ as the gate stack with L_G of 1 μm. (b) Trend of |I_D,max| enhancement and R_on reduction with L_G scaling.