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Surface passivation of GaN and GaN/AlGaN heterostructures by dielectric films and its application to insulated-gate heterostructure transistors

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Title: Surface passivation of GaN and GaN/AlGaN heterostructures by dielectric films and its application to insulated-gate heterostructure transistors
Authors: Hashizume, Tamotsu1 Browse this author →KAKEN DB
Ootomo, Shinya Browse this author
Inagaki, Takanori Browse this author
Hasegawa, Hideki Browse this author →KAKEN DB
Authors(alt): 橋詰, 保1
Issue Date: 5-Aug-2003
Publisher: AVS Science & Technology of Materials, Interfaces, and Processing
Journal Title: Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures
Volume: 21
Issue: 4
Start Page: 1828
End Page: 1838
Publisher DOI: 10.1116/1.1585077
Abstract: We have systematically investigated effects of plasma processing, formation of Si-based dielectrics, and formation of a thin Al2O3 film on the chemical and electronic properties of GaN and GaN/AlGaN heterostructure surfaces. The surface treatment in H2-plasma excited by electron-cyclotron-resonance (ECR) source, produced nitrogen-vacancy-related defect levels at GaN and AlGaN surfaces, while the ECR-N2-plasma treatment improved electronic properties of the surfaces. The deposition of a SiO2 film on GaN and AlGaN surfaces was found to induce high-density interface states, due to unexpected and uncontrollable oxidation reactions on the surfaces during the deposition process. In comparison, the SiNx/GaN passivation structure prepared by ECR-plasma assisted chemical vapor deposition showed good interface properties with the minimum Dit value of 1×1011 cm–2 eV–1. However, excess leakage currents governed by Fowler–Nordheim tunneling were observed in the SiNx/Al0.3Ga0.7N structure, due to a relatively small conduction band offset of 0.7 eV between SiNx and Al0.3Ga0.7N. A novel Al2O3-based passivation structure was proposed and fabricated by molecular beam deposition of Al and subsequent ECR O2-plasma oxidation. In situ x-ray photoelectron spectroscopy showed successful formation of the Al2O3 layer with a thickness of 3.5 nm and a large conduction band offset of 2.1 eV between Al2O3 and A0.3Ga0.7N. The GaN/AlGaN insulated-gate heterostructure field-effect transistors (IG HFETs) having the Al2O3-based passivation structure showed a good gate control of drain currents up to VGS = +3 V and achieved drain saturation current of 0.8 A/mm. The observed maximum gm value is 120 mS/mm. No current collapse was observed in the Al2O3 IG HFETs, indicating a remarkable advantage of the present Al2O3-based passivation structure.
Type: article
Appears in Collections:量子集積エレクトロニクス研究センター (Research Center for Integrated Quantum Electronics) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 橋詰 保

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