Cathodoluminescence study of h- and c-GaN single crystals grown by a Na or K flux

T. Sekiguchi, H. Yamane, M. Aoki, T. Araki, M. Shimada

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10 Citations (Scopus)


Luminescence properties of hexagonal (h-) and cubic (c-) GaN freestanding single crystals were studied by means of cathodoluminescence spectroscopy. The h-GaN crystals of about 0.2-2 mm in dimension were synthesized at 750°C by the reaction of Ga and N2 in a Na flux, while c-GaN crystals of about 0.3 mm or less in a K flux. The h-GaN showed rather strong band edge emission at room temperature compared with the crystal grown by using NaN3 as a nitrogen source. At 20 K, the band edge emission of h-GaN was split into four peaks. The main energy peak position was 3.478 eV, which was assigned as the A-free exciton emission. The energy position of the main peak of c-GaN was 3.268 eV. Assuming the binding energies of excitons in h- and c-GaN as 25 and 26 meV, respectively, the energy difference of bandgap between h- and c-GaN is estimated to be 209 meV. Since these crystals are free from strain from the substrates, the peak energies are reliable for the intrinsic GaN crystals. The full widths at half maximum of the emission of c-GaN were much broader than those of h-GaN, suggesting that the cubic phase is much defective compared with the hexagonal one.

Original languageEnglish
Pages (from-to)91-94
Number of pages4
JournalScience and Technology of Advanced Materials
Issue number2
Publication statusPublished - 2002 Mar


  • Cathodoluminescence
  • Cubic-GaN
  • Exciton
  • Flux growth
  • Hexagonal-GaN


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