【Domestic Papers】Simulation Study on Electrical Characteristics of NiO/β-Ga₂O₃ Heterojunction Enhancement Mode HJ-FinFET

      Researchers from the North University of China have published a dissertation titled "Simulation Study on Electrical Characteristics of NiO/β-Ga₂O₃ Heterojunction Enhancement Mode HJ-FinFET" in Crystals.

Project Support

      This research was supported by the Key Research and Development Program of Shanxi Province (Grant NO. 202302030201001) and Supported by the science and technology major Program of Shanxi Province (Grant NO. 202301030201003).

Background

      Due to the lack of effective P-type doping and low electron mobility, the voltage resistance of gallium oxide power devices is still far below the theoretical value and current research mainly focuses on exploring methods to alleviate the phenomenon of electric field concentration through small-sized devices, but there is relatively little research on large-sized high-power devices and their thermal stability. In addition, the low thermal conductivity of gallium oxide materials, coupled with complex intrinsic defect energy-level distribution, process defects, interface states, and oxide layer traps, lead to reliability issues such as electrical characteristic drift and accelerated performance degradation in gallium oxide devices.
In this paper, a novel Ga₂O₃ FinFET with NiO/n-Ga₂O₃ heterojunction (named Heterojunction FinFET: HJ-FinFET) for E-mode-type operation has been proposed. The p-NiO layer dramatically improves V_br; meanwhile, p-NiO/n-Ga₂O₃ forms an HJ and hetero-reduces the reverse conducting loss. It is expected that the proposed structure can cause the threshold voltage to shift to the right and realize the design of E-mode devices, and this device can be fabricated through ALD, MOCVD and lithography techniques.

Abstract

      In this paper, a novel enhancement-mode β-Ga₂O₃-based FinFET structure with a gate formed by the NiO/β-Ga₂O₃ heterojunction named HJ-FinFET has been proposed, and the excellent performance of the device has also been demonstrated. The primary operational mechanism of this structure involves integrating p-type NiO on both sides of the fin-shaped channel, which forms p-n junctions with β-Ga₂O₃. The depletion regions thus generated are utilized to establish electron channels, enabling enhancement-mode operation. The reverse p-NiO/n-Ga₂O₃ heterojunction diode is integrated to reduce the reverse free-wheeling loss. Compared with the conventional devices, the threshold voltage of the HJ-FinFET is greatly improved, and normally off operation is realized, showing a positive threshold voltage of 2.14 V. Meanwhile, the simulated breakdown voltage of the HJ-FinFET reaches 2.65 kV with specific on-resistance (R_on,sp) of 2.48 mΩ·cm² and the power figure of merit (PFOM = BV²/R_on,sp) reaches 2840 MW/cm², respectively. In addition, the influence of the doping concentration of the heterojunction layer constituting the gate, the doping concentration of the drift layer, and the channel width on the electrical characteristics of the devices were focused on. This structure provides a feasible idea for high-performance β-Ga₂O₃-based FinFET.

Conclusions

      In this work, a novel E-mode NiO/β-Ga₂O₃ HJ-FinFET has been proposed and investigated to achieve high-performance E-mode β-Ga₂O₃-based FinFETs. The influence of the doping concentration of the heterojunction layer constituting the gate, the doping concentration of the drift layer, and the channel width on the electrical characteristics of the devices were focused on. The simulation results shown that the width of the channel and the doping concentration of the β-Ga₂O₃ layer are the dominant factors affecting the device characteristics. By optimizing the relevant parameters, the device can operate stably in E-mode and a higher breakdown voltage was obtained. Ultimately, the device achieved a turn-on voltage of 2.14 V, a breakdown voltage of 2.65 kV, a low specific on-resistance (R_on,sp) of 2.48 mΩ·cm², and a high PFOM of 2840 MW/cm². In summary, the novel architecture proposed in this study effectively overcomes the common performance limitations of traditional lateral β-Ga₂O₃ MOSFETs. This advancement enables the realization of E-mode-type β-Ga₂O₃-based FinFET with low specific on-state resistance (R_on,sp) and high breakdown voltage, thus providing a new method for achieving high-performance power devices.