期刊
JOURNAL OF APPLIED PHYSICS
卷 127, 期 11, 页码 -出版社
AMER INST PHYSICS
DOI: 10.1063/1.5142766
关键词
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资金
- Innovation Fund Denmark under the project Semiconductor materials for power electronics-SEMPEL
In the current paper, the structure and properties of AlGaN/GaN interfaces are studied, explaining the role of AlGaN layer thickness on the two-dimensional electron gas (2DEG) formation. It is found that the generation of a continuous electron gas requires AlGaN films with stable stoichiometry, which can be reached only above a certain critical thickness, approximate to 6-7 nm in our case (20 at. % Al content). Thinner films are significantly affected by oxidation, which causes composition variations and structural imperfections leading to an inhomogeneity of the polarization field and, as a consequence, of the electron density across the interface. Using Kelvin probe force microscopy, this inhomogeneity can be visualized as variations of the surface potential on the sub-micrometer scale. For heterostructures with layer thickness above the critical value, the surface potential maps become homogeneous, reflecting a weakening influence of the oxidation on the interface electronic properties. The 2DEG formation is confirmed by the Hall measurements for these heterostructures.
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