In this letter, we design and demonstrate an improved metalorganic chemical vapor deposition (MOCVD) grown reverse Al-composition graded contact layer, whereby the Al-composition of AlxGa1−xN in the contact layer is graded from the higher Al-composition as in the channel to lower Al-composition, to achieve a low resistance contact to MOCVD grown ultrawide bandgap Al0.70Ga0.30N channel metal-semiconductor field-effect transistors. Increasing the thickness of the reverse graded layer was found to improve contact layer resistance significantly, leading to a contact resistivity of 3.3 × 10−5 Ω cm2. Devices with a gate length, LG, of 0.6 μm and a source-drain spacing, LSD, of 1.5 μm displayed a maximum current density, IDS,MAX, of 635 mA/mm with an applied gate voltage, VGS, of +2 V. Breakdown measurements on transistors with a gate to drain spacing, LGD, of 770 nm had breakdown voltage greater than 220 V, corresponding to a minimum breakdown field of 2.86 MV/cm—almost 3× higher than that exhibited by lateral GaN channel devices with similar dimensions. This work provides a framework for the design of low resistance contacts to MOCVD grown high Al-content AlxGa1−xN channel transistors.
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Design of compositionally graded contact layers for MOCVD grown high Al-content AlGaN transistors
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22 July 2019
Research Article|
July 25 2019
Design of compositionally graded contact layers for MOCVD grown high Al-content AlGaN transistors
Towhidur Razzak
;
Towhidur Razzak
a)
1
Department of Electrical and Computer Engineering, The Ohio State University
, Columbus, Ohio 43210, USA
a)Author to whom correspondence should be addressed: [email protected]
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Seongmo Hwang;
Seongmo Hwang
2
Department of Electrical Engineering, University of South Carolina
, 301 Main Street, Columbia, South Carolina 29208, USA
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Antwon Coleman;
Antwon Coleman
2
Department of Electrical Engineering, University of South Carolina
, 301 Main Street, Columbia, South Carolina 29208, USA
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Hao Xue;
Hao Xue
1
Department of Electrical and Computer Engineering, The Ohio State University
, Columbus, Ohio 43210, USA
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Shahadat H. Sohel;
Shahadat H. Sohel
1
Department of Electrical and Computer Engineering, The Ohio State University
, Columbus, Ohio 43210, USA
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Sanyam Bajaj;
Sanyam Bajaj
1
Department of Electrical and Computer Engineering, The Ohio State University
, Columbus, Ohio 43210, USA
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Yuewei Zhang;
Yuewei Zhang
1
Department of Electrical and Computer Engineering, The Ohio State University
, Columbus, Ohio 43210, USA
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Wu Lu;
Wu Lu
1
Department of Electrical and Computer Engineering, The Ohio State University
, Columbus, Ohio 43210, USA
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Asif Khan
;
Asif Khan
2
Department of Electrical Engineering, University of South Carolina
, 301 Main Street, Columbia, South Carolina 29208, USA
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Siddharth Rajan
Siddharth Rajan
1
Department of Electrical and Computer Engineering, The Ohio State University
, Columbus, Ohio 43210, USA
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a)Author to whom correspondence should be addressed: [email protected]
Appl. Phys. Lett. 115, 043502 (2019)
Article history
Received:
April 29 2019
Accepted:
July 07 2019
Citation
Towhidur Razzak, Seongmo Hwang, Antwon Coleman, Hao Xue, Shahadat H. Sohel, Sanyam Bajaj, Yuewei Zhang, Wu Lu, Asif Khan, Siddharth Rajan; Design of compositionally graded contact layers for MOCVD grown high Al-content AlGaN transistors. Appl. Phys. Lett. 22 July 2019; 115 (4): 043502. https://doi.org/10.1063/1.5108529
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