TY - JOUR
T1 - Two-dimensional electron gas at the AlGaN/GaN interface
T2 - Layer thickness dependence
AU - Popok, Vladimir N.
AU - Caban, Piotr A.
AU - Michalowski, Pawel Piotr
AU - Thorpe, Ryan
AU - Feldman, Leonard C.
AU - Pedersen, Kjeld
PY - 2020/3/21
Y1 - 2020/3/21
N2 - 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, ≈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.
AB - 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, ≈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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U2 - 10.1063/1.5142766
DO - 10.1063/1.5142766
M3 - Article
AN - SCOPUS:85082653929
VL - 127
JO - Journal of Applied Physics
JF - Journal of Applied Physics
SN - 0021-8979
IS - 11
M1 - 115703
ER -