| Original Articles |
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Growth and Characterization of AlGaN/AlN/GaN HEMT Structures with a Compositionally Step-Graded AlGaN Barrier Layer |
MA Zhi-Yong;WANG Xiao-Liang;HU Guo-Xin;RAN Jun-Xue;XIAO Hong-Ling;LUO Wei-Jun; TANG Jian;LI Jian-Ping;LI Jin-Min |
| Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 |
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| Cite this article: |
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MA Zhi-Yong, WANG Xiao-Liang, HU Guo-Xin et al 2007 Chin. Phys. Lett. 24 1705-1708 |
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Abstract A new AlGaN/AlN/GaN high electron mobility transistor (HEMT) structure using a compositionally step-graded AlGaN barrier layer is grown on sapphire by metalorganic chemical vapour deposition (MOCVD). The structure demonstrates significant enhancement of two-dimensional electron gas (2DEG) mobility and smooth surface morphology compared with the conventional HEMT structure with high Al composition AlGaN barrier. The high 2DEG mobility of 1806cm2/Vs at room temperature and low rms surface roughness of 0.220nm for a scan area of 5μm×5μm are attributed to the improvement of interfacial and crystal quality by employing the step-graded barrier to accommodate the large lattice mismatch stress. The 2DEG sheet density is independent of the measurement temperature, showing the excellent 2DEG confinement of the step-graded structure. A low average sheet resistance of 314.5Ω/square, with a good resistance uniformity of 0.68%, is also obtained across the 50mm epilayer wafer. HEMT devices are
successfully fabricated using this material structure, which exhibits a maximum extrinsic transconductance of 218mS/mm and a maximum drain current density of 800mA/mm.
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| Keywords:
73.40.Kp
81.15.Gh
84.30.Jc
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Received: 08 February 2007
Published: 17 May 2007
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| PACS: |
73.40.Kp
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(III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions)
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81.15.Gh
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(Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.))
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84.30.Jc
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(Power electronics; power supply circuits)
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