Two-dimensional electron gas at the AlGaN/GaN interface: Layer thickness dependence

Vladimir N. Popok, Piotr A. Caban, Pawel Piotr Michalowski, Ryan Thorpe, Leonard C. Feldman, Kjeld Pedersen

Research output: Contribution to journalArticle

Abstract

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.

Original languageEnglish
Article number115703
JournalJournal of Applied Physics
Volume127
Issue number11
DOIs
Publication statusPublished - Mar 21 2020

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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    Popok, V. N., Caban, P. A., Michalowski, P. P., Thorpe, R., Feldman, L. C., & Pedersen, K. (2020). Two-dimensional electron gas at the AlGaN/GaN interface: Layer thickness dependence. Journal of Applied Physics, 127(11), [115703]. https://doi.org/10.1063/1.5142766