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Open AccessArticle

Investigation of Recessed Gate AlGaN/GaN MIS-HEMTs with Double AlGaN Barrier Designs toward an Enhancement-Mode Characteristic

International College of Semiconductor Technology, National Chiao Tung University, Hsinchu 30010, Taiwan
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Author to whom correspondence should be addressed.
Micromachines 2020, 11(2), 163; https://doi.org/10.3390/mi11020163
Received: 31 December 2019 / Revised: 1 February 2020 / Accepted: 2 February 2020 / Published: 3 February 2020
(This article belongs to the Special Issue Wide Bandgap Based Devices: Design, Fabrication and Applications)
In this work, recessed gate AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs) with double AlGaN barrier designs are fabricated and investigated. Two different recessed depths are designed, leading to a 5 nm and a 3 nm remaining bottom AlGaN barrier under the gate region, and two different Al% (15% and 20%) in the bottom AlGaN barriers are designed. First of all, a double hump trans-conductance (gm)–gate voltage (VG) characteristic is observed in a recessed gate AlGaN/GaN MIS-HEMT with a 5 nm remaining bottom Al0.2Ga0.8N barrier under the gate region. Secondly, a physical model is proposed to explain this double channel characteristic by means of a formation of a top channel below the gate dielectric under a positive VG. Finally, the impacts of Al% content (15% and 20%) in the bottom AlGaN barrier and 5 nm/3 nm remaining bottom AlGaN barriers under the gate region are studied in detail, indicating that lowering Al% content in the bottom can increase the threshold voltage (VTH) toward an enhancement-mode characteristic.
Keywords: GaN; metal-insulator-semiconductor high-electron-mobility transistor (MIS-HEMT); recessed gate; double barrier GaN; metal-insulator-semiconductor high-electron-mobility transistor (MIS-HEMT); recessed gate; double barrier
MDPI and ACS Style

Wu, T.-L.; Tang, S.-W.; Jiang, H.-J. Investigation of Recessed Gate AlGaN/GaN MIS-HEMTs with Double AlGaN Barrier Designs toward an Enhancement-Mode Characteristic. Micromachines 2020, 11, 163.

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