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저희 연구실에서는 함께 연구할 석사 및 박사 과정 대학원생을 모집하고 있습니다.
SiC 및 WBG 전력반도체 소자 연구에 관심이 있다면,
아래 이메일로 연락 주세요: thkil [at] khu.ac.kr
Research Area
Our research focuses on interface engineering for wide-bandgap and ultra-wide-bandgap semiconductor devices in advanced power electronics.
We study gate dielectrics and dielectric/semiconductor interfaces as key design elements that govern device performance, reliability, and long-term stability.
Using SiC MOS systems as a core research platform, we aim to develop interface-engineering strategies that connect microscopic interface chemistry and bonding structures to macroscopic device properties and reliability. We further extend these concepts to emerging material systems such as Ga₂O₃.
SiC MOS Interface Analysis
Our SiC research focuses on how oxide/semiconductor interfaces control the electrical performance and reliability of power MOS devices.
In particular, nitridation of the SiO₂/4H-SiC interface is widely used to improve interface quality, but it can also modify band alignment, interface dipole formation, and voltage stability.
We examine these effects in SiC MOS structures to clarify how interfacial bonding and chemical modification influence flat-band voltage, threshold voltage, interface trap density, leakage behavior, and reliability.
The example shown below illustrates how nitrogen incorporation at the SiO₂/SiC interface can alter local bonding and modify the electrical response of MOS structures through interface-dipole formation. By analyzing how interface chemistry drives electrical-property modulation in MOS structures, we aim to build a broader framework for controlling dielectric/semiconductor interfaces in power devices.
Nitridation-induced interface modification in SiO₂/4H-SiC MOS structures.
Nitrogen incorporation at the SiO₂/SiC interface changes interfacial bonding and dipole formation, which can induce negative flat-band and threshold-voltage shifts in SiC MOS devices. [1]
Dipole Engineering in SiC MOS Devices
Building on our understanding of process-induced interface dipoles in SiC MOS structures, we further explore how dipoles can be intentionally engineered through dielectric-stack design.
Oxide/oxide interfaces, such as Al₂O₃/SiO₂ on 4H-SiC, provide a useful route for modulating electrostatic potential in MOS gate stacks without directly degrading the semiconductor channel interface.
The example shown below demonstrates how an additional Al₂O₃ layer can introduce an interface dipole at the Al₂O₃/SiO₂ interface, shifting the transfer characteristics of SiC MOSFETs toward a higher threshold voltage while maintaining field-effect mobility.
This concept represents a broader research direction in which gate-stack materials are engineered to control electrical properties, improve reliability, and optimize device performance.
Dipole engineering in Al₂O₃/SiO₂/SiC gate stacks.
An additional Al₂O₃ layer forms an interface dipole at the oxide/oxide interface (c), shifting the transfer characteristics toward a higher threshold voltage (a) while maintaining the field-effect mobility (b). [2]
Emerging Research on β-Ga₂O₃ MOS Structures
We are extending our interface-engineering approach from SiC to β-Ga₂O₃, an emerging ultra-wide-bandgap semiconductor for future power electronics.
β-Ga₂O₃ is attractive for high-electric-field applications, but its device performance and reliability strongly depend on the quality and stability of oxide/β-Ga₂O₃ interfaces. [3]
Our goal is to investigate how dielectric formation and oxide/β-Ga₂O₃ interface quality affect charge trapping, leakage behavior, and bias-temperature reliability in β-Ga₂O₃ MOS structures.
Rather than treating β-Ga₂O₃ as a separate topic, we view it as a new material platform where the interface-engineering concepts developed in SiC MOS systems can be tested, expanded, and refined.
Research expansion toward β-Ga₂O₃ MOS structures.
(a) Material-property comparison for Si, 4H-SiC, GaN, and Ga₂O₃, adapted from [3].
(b) Conceptual MOS capacitor structure for investigating oxide/β-Ga₂O₃ interfaces for power-device applications.
References
[1] T.-H. Kil and K. Kita, “Anomalous band alignment change of SiO₂/4H–SiC (0001) and (000–1) MOS capacitors induced by NO-POA and its possible origin,” Appl. Phys. Lett., vol. 116, no. 12, Art. no. 122103, Mar. 2020, doi: 10.1063/1.5135606.
[2] T.-H. Kil, M. Noguchi, H. Watanabe, and K. Kita, “Impacts of Al₂O₃/SiO₂ interface dipole layer formation on the electrical characteristics of 4H-SiC MOSFET,” IEEE Electron Device Lett., vol. 43, no. 1, pp. 92–95, Jan. 2022, doi: 10.1109/LED.2021.3125945.
[3] B. Mazumder and J. Sarker, “Probing structural and chemical evolution in (AlₓGa₁₋ₓ)₂O₃ using atom probe tomography: A review,” J. Mater. Res., vol. 36, no. 1, pp. 52–69, Jan. 2021, doi: 10.1557/s43578-020-00072-7.
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