Molecular beam epitaxy of GaN/AlxGa1-xN superlattices for 1.52-4.2 μm intersubband transitions

H. M. Ng, C. Gmachl, S. N.G. Chu, A. Y. Cho

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High-quality superlattice structures of GaN/AlGaN were grown on (0 0 0 1) sapphire substrates by molecular beam epitaxy. The threading dislocation density was reduced by growing low-temperature AlN layers in between the high-temperature GaN. In addition, in situ monitoring of the growth rate was achieved using pyrometric interferometry. Cross-sectional transmission electron microscopy of the superlattice structures revealed abrupt interfaces between GaN/AlGaN and excellent layer uniformity. We observed intersubband absorption at wavelengths as short as 1.52 μm in the GaN/AlGaN material system. A range of intersubband absorption peaks was observed between 1.52 and 4.2 μm by varying the well thickness and barrier Al content. In addition, the distribution of the built-in electric field between the well and barrier layers was also found to affect the intersubband transition wavelength.

Original languageEnglish (US)
Pages (from-to)432-438
Number of pages7
JournalJournal of Crystal Growth
Issue number4
StatePublished - Dec 2000
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Inorganic Chemistry
  • Materials Chemistry


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