【Member Papers】Ultralow On-Resistance High-Voltage β-Ga₂O₃ MOSFET With an Extended p-NiO Gate Field Plate

        Researchers from the University of Electronic Science and Technology of China have published a dissertation titled "Ultralow On-Resistance High-Voltage β-Ga₂O₃ MOSFET With an Extended p-NiO Gate Field Plate" in IEEE Transactions on Electron Devices.

Project Support

        This work was supported in part by the National Natural Science Foundation of China under Grant 62374028 and Grant 62404030, in part by the Postdoctoral Fellowship Program of China Postdoctoral Science Foundation (CPSF) under Grant GZC20240199 and Grant GZC20240200, and in part by the Central Government-Guided Local-Free Exploration Project under Grant 2023ZYD0160.

Background

        Ultrawide bandgap semiconductor β-Ga₂O₃ has exhibited extraordinary potential for next-generation power devices, owing to ultrawide bandgap of 4.5–4.9 eV, high critical electric field (E-field) ∼ 8 MV/cm, high Baliga’s figure-of-merit (BFOM = ε_sµ_nE³_c) and cost-effective growing methods. Over the past decade, β-Ga₂O₃ MOSFETs have attracted a great deal of attention due to the great advantages in power applications. Enormous efforts have been made to improve their power figure of merit (PFOM = breakdown voltage (BV)² /R_on,sp) by extreme-κ dielectrics, FinFET, superjunction, RESURF among others. Moreover, low-negative threshold voltage (V_th) value is required to reduce static power consumption and enhance circuit security in power conversion application. Gate recess heterojunction gate, current block layer (CBL) are effective solutions to improve the V_th. However, it is challenging to improve both R_on,sp and BV simultaneously because the high drift concentration for low R_on,sp easily leads to premature breakdown. In this work, we demonstrated and investigated a novel β-Ga₂O₃ MOSFET with an extended p-NiO gate field plate (PFP MOSFET) by Sentaurus TCAD. Different from common RESURF devices reducing the R_on,sp by assisted depletion effect to increase the N_d, the proposed device introduces the accumulation layer to further decrease the R_on,sp; therefore, the proposed PFP MOSFET can achieve a better trade-off between BV and R_on,sp.

Abstract

        A novel β-Ga₂O₃ MOSFET with an extended p-NiO gate field plate (PFP) is proposed and investigated. The extended p-NiO gate is separated from the Ga₂O₃ N-drift by Al₂O₃ dielectric layer and forms a metal/insulator/semiconductor (MIS) with Al₂O₃/Ga₂O₃ N-drift. In the on-state, a high-density electron layer is accumulated along the N-drift surface to provide an additional ultralow-resistance current path, and thus dramatically reduces specific on-resistance (R_on,sp). In the off-state, the PFP improves breakdown voltage (BV) by modulating the E -field distribution and assisting to deplete N-drift. Therefore, PFP MOSFET allows a higher N-drift doping concentration (N_d) to reduce R_on,sp without significant BV degradation. Compared with the MOSFET without PFP, the proposed device decreases the R_on,sp by 45% and increases the BV by 407%, resulting in a high PFOM up to 1.63 GW/cm². This work provides a new insight into realizing a high-performance β-Ga₂O₃ MOSFET for future power conversion applications.

Conclusion

        An ultralow R_on,sp and high BV β-Ga₂O₃ MOSFET is proposed and investigated. The proposed MOSFET features an extended p-NiO gate field plate (PFP). The PFP induces an electron accumulation layer in the ON-state to achieve an ultralow R_on,sp and modulates E-field distribution to enhance BV in the OFF-state. By optimizing key parameters, PFP MOSFET exhibit R_on,sp of 6.4 mΩ · cm² and BV of 3230 V, resulting in a high PFOM up to 1.63 GW/cm². Compared with PG MOSFET, the R_on,sp and BV of the PFP MOSFET are improved by 45% and 407%, respectively; therefore, the PFP MOSFET achieves better trade-off between R_on,sp and BV, exhibiting extraordinary figure of merit.