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22 results on '"Wu, Changtong"'

4. Fabrication and formation mechanisms of ohmic conducts with low annealing temperature for GaN/AlN superlattice barrier HEMTs.

Author

Li, Shanjie, Wu, Changtong, Zeng, Fanyi, Wu, Nengtao, Luo, Ling, Cao, Ben, Wang, Wenliang, and Li, Guoqiang

Subjects
*MODULATION-doped field-effect transistors, *TWO-dimensional electron gas, *RADIO frequency, *OHMIC resistance, *OHMIC contacts, *GALLIUM nitride
Abstract

This work investigates the Ohmic contact mechanism and low resistance Ohmic contact preparation for GaN-based high electron mobility transistors (HEMTs) with GaN/AlN superlattice (SL) barriers. The electrical and microstructural characterization of Ti/Al/Ni/Au contacts shows that the formation of Ohmic contacts primarily depends on the TiN islands formed by Ti diffusion in the barrier layer, which is the main reason for the high contact resistance of GaN/AlN SLs HEMTs under conventional high-temperature annealing. A grid deep-recess technique is proposed to establish direct contact between TiN interfacial layer, the barrier, and the two-dimensional electron gas through the sidewalls. This novel technique achieves an Ohmic contact with a low contact resistance of 0.31 Ω mm at low temperatures (700 °C). Furthermore, increased grid deep-recess density effectively reduces contact resistance due to the additional contribution from the conduction width. It is also noteworthy that after complete removal of the barrier layer, the impact of recess depth on contact characteristics is minimal, greatly reducing the process complexity of grid deep-recess technique. Consequently, GaN/AlN SLs HEMTs fabricated using the grid deep-recess technique exhibit significant improvements in on-resistance, transconductance and saturation current. These results are expected to expand the potential application of GaN/AlN SL barrier layers in radio frequency and power devices. [ABSTRACT FROM AUTHOR]

Published
2025
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7. High On/Off Current Ratio and High Vth/Ron Stability GaN MIS-HEMTs With GaN/AlN Superlattices Barrier

Author

Li, Shanjie, Zeng, Fanyi, Xing, Zhiheng, Wu, Nengtao, Cao, Ben, Luo, Ling, Wu, Changtong, Wang, Wenliang, and Li, Guoqiang

Abstract

In this work, the electrical characteristics and bias stress reliability of GaN/AlN superlattices (SLs) metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) with Al2O3 dielectric are experimentally investigated. In comparison to the conventional AlGaN barrier MIS-HEMTs, the GaN/AlN SLs MIS-HEMTs exhibit a higher ON/OFF current ratio ( $10^{{{10}}}$ ), higher gate forward breakdown voltage (BV) (15.2 V) and OFF -state BV (495 V), lower ON-resistance ( $9.5~\Omega $ /mm $^{{-{1}}}$ ). Moreover, the threshold voltage ( $V_{{\text {th}}}$ ) shift and ON-resistance (R on) degradation under bias stress are further monitored. The GaN/AlN SLs MIS-HEMTs demonstrate excellent $V_{{\text {th}}}$ and $R_{{\text {on}}}$ stability, attributed to the superior dielectric/barrier interface quality and effective 2-D electron gas confinement provided by the GaN/AlN superlattice structure. These results ensure the superior performance and stability of GaN/AlN SLs MIS-HEMTs for power/RF applications.

Published
2024
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8. Enhanced Performance of Low-Leakage-Current Normally off p-GaN Gate HEMTs Using NH3 Plasma Pretreatment

Author

Wu, Nengtao, Luo, Ling, Xing, Zhiheng, Li, Shanjie, Zeng, Fanyi, Cao, Ben, Wu, Changtong, and Li, Guoqiang

Abstract

In this article, a low-leakage-current and high-breakdown-voltage normally OFF p-GaN gate high-electron-mobility transistor (HEMT) on a Si substrate with low-damage NH3 plasma pretreatment was investigated. NH3 plasma pretreatment was performed in a plasma-enhanced chemical vapor deposition (PECVD) system before PECVD-SiNx deposition, which effectively removed surficial oxides and other impurities, suppressed the interface traps between those of SiNx and (Al)GaN, and reduced the overall drain leakage current of devices in the OFF-state. In comparison to the device without pretreatment, the normally OFF p-GaN gate HEMTs pretreated with NH3 plasma exhibited a high ON/OFF-current ratio of $10^{{9}}$ , a low reverse gate leakage current of $2.86\times 10^{-{8}}$ mA/mm, a high gate breakdown voltage of 9.1 V, and a high breakdown voltage of 690 V at $1~\mu \text{A}$ /mm. Furthermore, NH3 plasma pretreatment effectively suppressed the threshold voltage shift induced by the charge/discharge effect in p-GaN. It was found that NH3 plasma pretreatment is effective in improving device performance, such as the leakage current, breakdown voltage, and threshold voltage stability.

Published
2023
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