Dr. Dongkyu Lee Profile

Dr. Dongkyu Lee

at Univ of South Carolina

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Publications (2)

Proceedings Article | 15 March 2023 Presentation + Paper

Gate leakage current and threshold voltage characteristics of β-Ga2O3 passivated AlGaN/GaN based heterojunction field effect transistor

Samiul Hasan, Mohi Uddin Jewel, Scott Crittenden, Dongkyu Lee, Vitaliy Avrutin, Ümit Özgür, Hadis Morkoç, Iftikhar Ahmad

Proceedings Volume 12421, 124210A (2023) https://doi.org/10.1117/12.2668236

KEYWORDS: Dielectrics, Gallium nitride, Heterojunctions, Field effect transistors, Oxides, Passivation, Gallium, Metalorganic chemical vapor deposition, Interfaces, Capacitance

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Proceedings Article | 4 October 2022 Presentation + Paper

Investigation of Ni/Y2O3/n-4H-SiC metal-oxide-semiconductor structure for high-resolution radiation detection

OmerFaruk Karadavut, Ritwik Nag, Josh Kleppinger, Gene Yang, Dongkyu Lee, Sandeep Chaudhuri, Krishna Mandal

Proceedings Volume 12241, 1224107 (2022) https://doi.org/10.1117/12.2635949

KEYWORDS: Sensors, Silicon carbide, Capacitance, Dielectrics, Oxides

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Ni/Y₂O₃/4H-SiC metal-oxide-semiconductor (MOS) structure has been realized on 20 μm thick 4H-SiC epitaxial layers by depositing 40 nm thick Y₂O₃ layers through pulsed laser deposition and using nickel as the gate contact. 4H-SiC based MOS structures with thin oxide layers are being considered as novel detector structures for ionizing radiation. Y₂O₃ being a wide bandgap (5.5 eV) and high-𝑘 dielectric (𝑘 = 14-16) is beneficial to lower the junction leakage current and increasing the bias voltage limit. The current-voltage (I-V) characteristics recorded for the fabricated MOS devices revealed excellent rectification properties and a very low leakage current density of 80 pA/cm² at a gate bias of -500 V. The Mott-Schottky plot obtained from high frequency (1 MHz) capacitance-voltage (C-V) measurement revealed a linear trend as observed in Ni/4H-SiC Schottky barrier detectors. A built-in potential of ≈2.0 V has been calculated from the C-V characteristics. The radiation detection properties of the MOS detectors have been assessed through pulse height spectroscopy using a ²⁴¹Am alpha particle source. The detectors revealed a well-defined peak in the pulse height spectrum with an energy resolution of 1.6% and a charge collection efficiency (CCE) of 82% at 0 V applied bias (self-biased mode) for the 5486 keV alpha particles. The energy resolution and the charge collection efficiency were seen to improve further with increased gate bias. A CCE of 1.0 and an energy resolution of 0.4% has been observed when the MOS detector was biased at -50 V. A very long hole diffusion length of 56 μm has been calculated using a drift-diffusion model and the variation of experimentally obtained CCE with bias voltage. Such long hole diffusion length and the high built-in potential has led to the highefficiency detection performance in self-biased mode. Capacitance-mode deep level transient spectroscopy revealed the presence of deep level trap centers commonly observed in 4H-SiC epilayers with trap concentrations similar to that has been observed in our previous devices.

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