Fixed interface charges between AlGaN barrier and gate stack composed of in situ grown SiN and Al{sub 2}O{sub 3} in AlGaN/GaN high electron mobility transistors with normally off capability
- Institute of Solid State Electronics, Vienna University of Technology, Floragasse 7, 1040 Vienna (Austria)
- EpiGaN, Kempischesteenweg 293, 3500 Hasselt (Belgium)
Using a generalized extraction method, the fixed charge density N{sub int} at the interface between in situ deposited SiN and 5 nm thick AlGaN barrier is evaluated by measurements of threshold voltage V{sub th} of an AlGaN/GaN metal insulator semiconductor high electron mobility transistor as a function of SiN thickness. The thickness of the originally deposited 50 nm thick SiN layer is reduced by dry etching. The extracted N{sub int} is in the order of the AlGaN polarization charge density. The total removal of the in situ SiN cap leads to a complete depletion of the channel region resulting in V{sub th} = +1 V. Fabrication of a gate stack with Al{sub 2}O{sub 3} as a second cap layer, deposited on top of the in situ SiN, is not introducing additional fixed charges at the SiN/Al{sub 2}O{sub 3} interface.
- OSTI ID:
- 22257738
- Journal Information:
- Applied Physics Letters, Journal Name: Applied Physics Letters Journal Issue: 11 Vol. 104; ISSN APPLAB; ISSN 0003-6951
- Country of Publication:
- United States
- Language:
- English
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