Effect of Atomic-Layer-Deposition Method on Threshold Voltage Shift in AlGaN/GaN Metal--Insulator--Semiconductor High Electron Mobility Transistors

We have investigated the mechanism for threshold voltage ($V_{\text{th}}$) shift of AlGaN/GaN metal--insulator--semiconductor high electron mobility transistors (MIS-HEMTs) for power applications. In this study, atomic layer deposited (ALD)-Al 2 O 3 was used in AlGaN/GaN MIS-HEMTs as gate insulator...

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Published inJapanese Journal of Applied Physics Vol. 52; no. 11; pp. 11NG04 - 11NG04-4
Main Authors Ozaki, Shiro, Ohki, Toshihiro, Kanamura, Masahito, Okamoto, Naoya, Kikkawa, Toshihide
Format Journal Article
LanguageEnglish
Published The Japan Society of Applied Physics 01.11.2013
Subjects
Aluminum gallium nitrides
Aluminum oxide
Damage
Gallium nitrides
Gates
High electron mobility transistors
Oxidants
Semiconductor devices
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Summary:We have investigated the mechanism for threshold voltage ($V_{\text{th}}$) shift of AlGaN/GaN metal--insulator--semiconductor high electron mobility transistors (MIS-HEMTs) for power applications. In this study, atomic layer deposited (ALD)-Al 2 O 3 was used in AlGaN/GaN MIS-HEMTs as gate insulator films, and we focused on plasma-induced damages at the GaN/Al 2 O 3 interface, when O 2 plasma was used as the oxidant source for the ALD method. We clarified that the deep trap sites which were located around 2.58--3.26 eV from the conduction band edge were generated in the oxidized-GaN layer at the GaN/Al 2 O 3 interface due to plasma-induced damages, and this caused the $V_{\text{th}}$ shift when using O 2 plasma. Therefore, we controlled the initial oxidant source, and demonstrated the reductions in the $V_{\text{th}}$ shift and the gate leakage current by applying hybrid--Al 2 O 3 structure (lower H 2 O vapor--Al 2 O 3 /upper O 2 plasma--Al 2 O 3 ) for AlGaN/GaN MIS-HEMTs.
Bibliography:(Color online) Schematic cross-sectional view of normally-on type AlGaN/GaN MIS-HEMTs structure used in this work. (Color online) (a) $C$--$V$ curves of AlGaN/GaN MIS-HEMTs obtained at before and after light irradiation. (b) Schematic illustrations for photo-ionization of captured electrons under light irradiation. (Color online) Depth profile of GaN oxidation at GaN/Al 2 O 3 interface for O 2 plasma--Al 2 O 3 and H 2 O vapor--Al 2 O 3 measured by XPS. (Color online) $C$--$V$ curves of AlGaN/GaN MIS-HEMTs obtained before and after light irradiation when using O 2 plasma--Al 2 O 3 (a) and H 2 O vapor--Al 2 O 3 (b). Photon energy was applied at 3.26 eV. (Color online) Relationship between wavelength and $V_{\text{th}}$ shift of AlGaN/GaN MIS-HEMT measured by DLOS. (Color online) Schematic cross-sectional view of proposed mechanism for $V_{\text{th}}$ shift of AlGaN/GaN MIS-HEMT due to GaN oxidation when using O 2 plasma--Al 2 O 3 . (Color online) Schematic cross-sectional view of normally-on type AlGaN/GaN MIS-HEMTs using hybrid--Al 2 O 3 structure. (Color online) $I_{\text{ds}}$--$V_{\text{gs}}$ characteristics of AlGaN/GaN MIS-HEMTs using O 2 plasma--Al 2 O 3 , H 2 O vapor--Al 2 O 3 , and hybrid--Al 2 O 3 . (Color online) $I_{\text{g}}$--$V_{\text{gs}}$ characteristics of AlGaN/GaN MIS-HEMTs using O 2 plasma--Al 2 O 3 , H 2 O vapor--Al 2 O 3 , and hybrid--Al 2 O 3 .
ObjectType-Article-1
SourceType-Scholarly Journals-1
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ISSN:0021-4922
1347-4065
DOI:10.7567/JJAP.52.11NG04