Free carrier accumulation at cubic AlGaN/GaN heterojunctions

Q. Y. Wei, T. Li, J. Y. Huang, Fernando Ponce, E. Tschumak, A. Zado, D. J. As

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Abstract

Cubic Al 0.3Ga 0.7N/GaN heterostructures were grown by plasma-assisted molecular beam epitaxy on 3C-SiC (001) substrates. A profile of the electrostatic potential across the cubic-AlGaN/GaN heterojunction was obtained using electron holography in the transmission electron microscope. The experimental potential profile indicates that the unintentionally doped layers show n-type behavior and accumulation of free electrons at the interface with a density of 5.1×10 11/cm 2, about one order of magnitude less than in wurtzite AlGaN/GaN junctions. A combination of electron holography and cathodoluminescence measurements yields a conduction-to-valence band offset ratio of 5:1 for the cubic AlGaN/GaN interface, which also promotes the electron accumulation. Band diagram simulations show that the donor states in the AlGaN layer provide the positive charges that to a great extent balance the two-dimensional electron gas.

Original languageEnglish (US)
Article number142108
JournalApplied Physics Letters
Volume100
Issue number14
DOIs
StatePublished - Apr 2 2012

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ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)

Cite this

Wei, Q. Y., Li, T., Huang, J. Y., Ponce, F., Tschumak, E., Zado, A., & As, D. J. (2012). Free carrier accumulation at cubic AlGaN/GaN heterojunctions. Applied Physics Letters, 100(14), [142108]. https://doi.org/10.1063/1.3700968