In this presentation, we will review recent work on the integration of high permittivity dielectrics with wide and and ultra-wide bandgap semiconductor devices to obtain improved high power and high frequency applications. We will first discuss the use of such structures for vertical power devices. The high permittivity dielectrics help to reduce surface fields and therefore prevent tunnel leakage from Schottky barriers [1]. Insertion of high permittivity dielectrics can also enable better field termination in high voltage vertical devices [2]. We will discuss recent results using such high permittivity dielectrics in vertical device structures based on Gallium Oxide, leading to high vertical electric fields up to 5.7 MV/cm being sustained in the structure.

We will discuss the application of these high permittivity dielectrics for three-terminal high frequency [3] and high voltage [4,5] wide bandgap transistor applications. In lateral transistors built from wide and ultra-wide bandgap semiconductors, gate breakdown and non-uniform electric fields lead to average device breakdown fields that are significantly lower than material limits. We will show how high permittivity dielectrics inserted between the gate and drain can prevent gate breakdown, and also create much more uniform electric field profiles. An analytical model to explain this will be presented and compared with 2-dimensional device simulations.

Finally, we will show experimental results for lateral devices from the high Al-composition AlGaN [6], -Ga₂O₃[7], and AlGaN/GaN [8] material systems, where in each case, we are able to achieve state-of-art breakdown performance for devices such as lateral Schottky diodes and transistors. For example, we have achieved up to 8.3 MV/cm field in high Al-content AlGaN devices, >5.5 MV/cm in -Ga₂O₃-based transistors, and >3 MV/cm lateral electric field in AlGaN/GaN HEMTs. The high breakdown fields also enable us to achieve state-of-art switching figures of merit in these devices.

The authors acknowledge funding from NNSA ETI Consortium, AFOSR GAME MURI Program (Program Manager Dr. Ali Sayir), AFOSR (Program Manager Dr. Kenneth Goretta) NSF ECCS- and the DARPA DREAM program (Program Manger Dr. YK Chen), managed by ONR (Program Manager Dr. Paul Maki) for support of the work.

References

[1] Xia, Zhanbo, et al. "Metal/BaTiO₃/β-Ga₂O₃ dielectric heterojunction diode with 5.7 MV/cm breakdown field." Applied Physics Letters 115.25 (2019): 252104.

[2] Lee, Hyun-Soo, et al. "High-permittivity dielectric edge termination for vertical high voltage devices." Journal of Computational Electronics 19.4 (2020): 1538-1545.

[3] Xia, Zhanbo, et al. "Design of transistors using high-permittivity materials." IEEE Transactions on Electron Devices 66.2 (2019): 896-900.

[4] Kalarickal, Nidhin Kurian, et al. "Electrostatic engineering using extreme permittivity materials for ultra-wide bandgap semiconductor transistors." IEEE Transactions on Electron Devices 68.1 (2020): 29-35.

[5] Hanawa, Hideyuki, et al. "Numerical Analysis of Breakdown Voltage Enhancement in AlGaN/GaN HEMTs With a High-k Passivation Layer." IEEE Transactions on Electron Devices 61.3 (2014): 769-775.

[6] Razzak, Towhidur, et al. "BaTiO₃/Al_{0. 58}Ga_{0. 42}N lateral heterojunction diodes with breakdown field exceeding 8 MV/cm." Applied Physics Letters 116.2 (2020): 023507.

[7] Kalarickal, Nidhin Kurian, et al. "β-(Al_0.18Ga_0.82)₂O₃/Ga₂O₃ Double Heterojunction Transistor With Average Field of 5.5 MV/cm." IEEE Electron Device Letters 42.6 (2021): 899-902.

[8] Rahman, Mohammad Wahidur, et al. "Hybrid BaTiO₃/SiN_x/AlGaN/GaN lateral Schottky barrier diodes with low turn-on and high breakdown performance." Applied Physics Letters 119.1 (2021): 013504.