【Member Papers】A Novel 2.7 kV 3C-SiC/Ga₂O₃ Hetero-Channel E-mode MISFET With BFOM up to 5.17 GW/cm²

      Researchers from the University of Electronic Science and Technology of China have published a dissertation titled "A Novel 2.7 kV 3C-SiC/Ga₂O₃ Hetero-Channel E-mode MISFET With BFOM up to 5.17 GW/cm²" in Microelectronics Journal.

Background

      β-Ga₂O₃ represents the most stable crystalline form of gallium oxide and is considered as a promising material for next-generation power devices due to its ultra-wide bandgap of 4.4-4.9 eV, high critical breakdown electric field (∼ 8 MV/cm). Despite these favorable characteristics, the absence of efficient p-type dopants in Ga₂O₃ remains a critical obstacle for high-voltage enhancement-mode (E-mode) metal-insulator-semiconductor field-effect transistors (MISFET). Several researches have been explored to fabricate E-mode high-voltage vertical MISFET, like current apertures and trench structures with high-resistivity layers, such as nitrogen-implantation or magnesium doped. However, the high-resistivity region causes unacceptable leakage current and increased specific on-resistance (R_on,sp). Fin-gate MISFET (FG-MISFET) has shown promising capabilities in achieving E-mode operation, reduced leakage current and high BV (The highest BV reaches 2.66 kV [10]). Another obstacle of MISFET is lack of an efficient electric field shielding structure, which causes pre-breakdown and reliability issues in the gate oxide. Similar to SiC MOSFET, the critical electric field (E_C) in the gate oxide of Ga₂O₃ MISFET should be restricted to less than one-third of its theoretical value, which is approximately 5.3 MV/cm for Al₂O₃.

Abstract

      In this letter, a novel 3C-SiC/Ga₂O₃ Hetero-Channel Ga₂O₃ MISFET (3C-HC-MISFET) for enhancement-mode (E-mode) operation, low specific on-resistance (R_on,sp) and low reverse on-state voltage drop (V_{R_ON}) is proposed and demonstrated by experimentally calibrated TCAD. A p-type 3C-SiC layer is directly bonded atop β-Ga₂O₃ to form the inversion channel for E-mode operation. A heavily doped p-NiO layer under the trench gate suppresses the electric field in the gate dielectric. Besides, the p-NiO/Ga₂O₃ interface forms a low-barrier Heterojunction diode (HJD), which significantly reduces V_{R_ON}. The simulated BV of the 3C-HC-MISFET reaches ∼2.7 kV with R_on,sp being only 1.44 mΩ·cm², 12% lower than that of the GaN limit. Compared to the conventional Fin-gate MISFET (FG-MISFET), Baliga’s Figure of Merit of the 3C-HC-MOSFET reaches 5.17 GW/cm², which is improved by 320%. Moreover, the maximum temperature rise (T_rmax) of the proposal under the continuous current-pulse test reduces by 29 K compared to FG-MISFET. Therefore, the 3C-HC-MOSFET is a promising candidate for high-voltage E-mode Ga₂O₃ power devices.

Conclusion

      A novel high-voltage E-mode Ga₂O₃ MISFET with ultra-low R_on,sp, breaking GaN limit is proposed. A 3C-SiC layer with high channel mobility is used as channel region. A p-NiO layer at the bottom of the gate is employed to protect the gate oxide Al₂O₃ and 3C-SiC from pre-breakdown, thereby increasing the BV and reliability. Compared to FG-MISFET, 3C-HC-MISFET yields a high BFOM of 5.17 GW/cm², 12% higher than that of GaN limit. The V_{R_on} is reduced by 2.33 V. Besides, C_GD of 3C-HC-MISFET is significantly reduced. Moreover, the maximum temperature rise under forward and reverse conduction states are significantly reduced by 29 K and 33 K, respectively. These properties make it an ideal candidate for future high-performance power electronics applications.