Properties of GaN epilayers grown on misoriented sapphire substrates

Carol Trager-Cowan, S. McArthur, P. G. Middleton, K. P. O'Donnell, D. Zubia, S. D. Hersee

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Three silicon-doped 3 μm thick GaN epilayers were grown simultaneously by metalorganic chemical vapour deposition on (0001 ) sapphire substrates misorientated by 0°, 4° and 10° toward the m-plane (101̄0). A comparative study of these epilayers was undertaken using photoluminescence (PL) spectroscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM), cathodoluminescence (CL) imaging, CL spectroscopy and Hall effect measurements. Low temperature PL of the 0° and 4° epilayers shows donor bound exciton (BE) emission between 3.47 and 3.48 eV and a low level of yellow band emission. The peak intensities of both emission bands are a factor of 2 higher for the 4° layer. In the 10° epilayer, the BE band is 3x stronger than in the 0° epilayer but there is no discernible yellow band. However, a number of additional bands appear at 3.459, 3.417, 3.362, 3.345, 3.309, and 3.285 eV. These bands, some of which are acceptor related, may be attributed to the presence of structural defects in this epilayer, pointing to an abrupt degradation of its structural quality compared to the others. This degradation is confirmed by AFM studies. On a 20 μm × 20 μm image the 0° and 4° epilayers exhibit smooth surface morphologies, while the 10° epilayer shows a high density of hexagonal pits. Finally, SEM images reveal the surface of the 10° epilayer to be "streaked" and pitted. Low temperature CL images at 3.48 eV (bound exciton region) show random spotty emission, while those at 3.28 eV and 3.41 eV exhibit a streaky appearance similar to the SEM image. This suggests that these luminescence bands are indeed associated with structural defects.

LanguageEnglish
Article numbere36
JournalMRS Internet Journal of Nitride Semiconductor Research
Volume3
DOIs
Publication statusPublished - 1 Dec 1998

Fingerprint

sapphire
cathodoluminescence
excitons
scanning electron microscopy
atomic force microscopy
degradation
photoluminescence
defects
spectroscopy
metalorganic chemical vapor deposition
Hall effect
luminescence
silicon

Keywords

  • nitrides
  • substrates
  • luminescence
  • imaging

Cite this

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title = "Properties of GaN epilayers grown on misoriented sapphire substrates",
abstract = "Three silicon-doped 3 μm thick GaN epilayers were grown simultaneously by metalorganic chemical vapour deposition on (0001 ) sapphire substrates misorientated by 0°, 4° and 10° toward the m-plane (101̄0). A comparative study of these epilayers was undertaken using photoluminescence (PL) spectroscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM), cathodoluminescence (CL) imaging, CL spectroscopy and Hall effect measurements. Low temperature PL of the 0° and 4° epilayers shows donor bound exciton (BE) emission between 3.47 and 3.48 eV and a low level of yellow band emission. The peak intensities of both emission bands are a factor of 2 higher for the 4° layer. In the 10° epilayer, the BE band is 3x stronger than in the 0° epilayer but there is no discernible yellow band. However, a number of additional bands appear at 3.459, 3.417, 3.362, 3.345, 3.309, and 3.285 eV. These bands, some of which are acceptor related, may be attributed to the presence of structural defects in this epilayer, pointing to an abrupt degradation of its structural quality compared to the others. This degradation is confirmed by AFM studies. On a 20 μm × 20 μm image the 0° and 4° epilayers exhibit smooth surface morphologies, while the 10° epilayer shows a high density of hexagonal pits. Finally, SEM images reveal the surface of the 10° epilayer to be {"}streaked{"} and pitted. Low temperature CL images at 3.48 eV (bound exciton region) show random spotty emission, while those at 3.28 eV and 3.41 eV exhibit a streaky appearance similar to the SEM image. This suggests that these luminescence bands are indeed associated with structural defects.",
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year = "1998",
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Properties of GaN epilayers grown on misoriented sapphire substrates. / Trager-Cowan, Carol; McArthur, S.; Middleton, P. G.; O'Donnell, K. P.; Zubia, D.; Hersee, S. D.

In: MRS Internet Journal of Nitride Semiconductor Research, Vol. 3, e36, 01.12.1998.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Properties of GaN epilayers grown on misoriented sapphire substrates

AU - Trager-Cowan, Carol

AU - McArthur, S.

AU - Middleton, P. G.

AU - O'Donnell, K. P.

AU - Zubia, D.

AU - Hersee, S. D.

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AB - Three silicon-doped 3 μm thick GaN epilayers were grown simultaneously by metalorganic chemical vapour deposition on (0001 ) sapphire substrates misorientated by 0°, 4° and 10° toward the m-plane (101̄0). A comparative study of these epilayers was undertaken using photoluminescence (PL) spectroscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM), cathodoluminescence (CL) imaging, CL spectroscopy and Hall effect measurements. Low temperature PL of the 0° and 4° epilayers shows donor bound exciton (BE) emission between 3.47 and 3.48 eV and a low level of yellow band emission. The peak intensities of both emission bands are a factor of 2 higher for the 4° layer. In the 10° epilayer, the BE band is 3x stronger than in the 0° epilayer but there is no discernible yellow band. However, a number of additional bands appear at 3.459, 3.417, 3.362, 3.345, 3.309, and 3.285 eV. These bands, some of which are acceptor related, may be attributed to the presence of structural defects in this epilayer, pointing to an abrupt degradation of its structural quality compared to the others. This degradation is confirmed by AFM studies. On a 20 μm × 20 μm image the 0° and 4° epilayers exhibit smooth surface morphologies, while the 10° epilayer shows a high density of hexagonal pits. Finally, SEM images reveal the surface of the 10° epilayer to be "streaked" and pitted. Low temperature CL images at 3.48 eV (bound exciton region) show random spotty emission, while those at 3.28 eV and 3.41 eV exhibit a streaky appearance similar to the SEM image. This suggests that these luminescence bands are indeed associated with structural defects.

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