Growth and Characterization of A1GaN/A1N/GaN HEMT Structures with a Compositionally Step-Graded A1GaN Barrier Layer  

作　　者：马志勇 王晓亮 胡国新 冉军学 肖红领 罗卫军 唐健 李建平 李晋闽 

机构地区：[1]Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083

出　　处：《Chinese Physics Letters》2007年第6期1705-1708,共4页中国物理快报（英文版）

基　　金：Supported by the Knowledge Innovation Project of Chinese Academy of Sciences （No KGCX2-SW-107-1）, the National Natural Science Foundation of China under Grant No 60606002, the State Key Basic Research Programme of China under Grant Nos 2002CB311903, 2006CB604905, and 513270505.

摘　　要：A new A1GaN/A1N/GaN high electron mobility transistor （HEMT） structure using a compositionally step-graded A1GaN 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 A1 composition A1GaN barrier. The high 2DEG mobility of 1806 cm2/Vs at room temperature and low rms surface roughness of 0.220 nm for a scan area of 5μm×5 μm are attributed to the improvement of interracial and crystal quality by employing the stepgraded 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 50 mm epilayer wafer. HEMT devices are successfully fabricated using this material structure, which exhibits a maximum extrinsic transconductance of 218 mS/ram and a maximum drain current density of 800 mA/mm.A new A1GaN/A1N/GaN high electron mobility transistor （HEMT） structure using a compositionally step-graded A1GaN 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 A1 composition A1GaN barrier. The high 2DEG mobility of 1806 cm2/Vs at room temperature and low rms surface roughness of 0.220 nm for a scan area of 5μm×5 μm are attributed to the improvement of interracial and crystal quality by employing the stepgraded 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 50 mm epilayer wafer. HEMT devices are successfully fabricated using this material structure, which exhibits a maximum extrinsic transconductance of 218 mS/ram and a maximum drain current density of 800 mA/mm.

分 类 号：O47[理学—半导体物理]