The role of surface kinetics on composition and quality of AlGaN

Isaac Bryan, Zachary Bryan, Seiji Mita, Anthony Rice, Lindsay Hussey, Christopher Shelton, James Tweedie, Jon Paul Maria, Ramón Collazo, Zlatko Sitar

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Abstract

Metal–polar, Al-rich AlGaN films were grown on both single crystalline AlN and sapphire substrates. The role of surface morphology and surface kinetics on AlGaN composition is presented. With the reduced dislocation density of the films grown on AlN substrates, atomically smooth bilayer stepped surfaces are achieved with RMS roughness of less than 50 pm for a 5×5 µm2 AFM scan area. By controlling the surface supersaturation through adjusting the growth rate, a transition from 2D nucleation to step flow was observed. The critical misorientation angle for step-bunching in nominal Al0.70Ga0.30N grown with a growth rate of 600 nm/h on AlN substrates was found to be 0.4°. The composition of bilayer stepped AlGaN was strongly dependent on substrate misorientation angle, where a compositional variation by a factor of two for a change in misorientation angle from 0.05 to 0.40° was observed; this is explained by the different surface diffusion lengths of Ga and Al. Step-bunching resulted in strong compositional inhomogeneity as observed by photoluminescence and scanning transmission electron microscopy studies.

Original languageEnglish (US)
Pages (from-to)65-71
Number of pages7
JournalJournal of Crystal Growth
Volume451
DOIs
StatePublished - Oct 1 2016

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All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Inorganic Chemistry
  • Materials Chemistry

Cite this

Bryan, I., Bryan, Z., Mita, S., Rice, A., Hussey, L., Shelton, C., Tweedie, J., Maria, J. P., Collazo, R., & Sitar, Z. (2016). The role of surface kinetics on composition and quality of AlGaN. Journal of Crystal Growth, 451, 65-71. https://doi.org/10.1016/j.jcrysgro.2016.06.055