Electron microscopy characterization of GaN films grown by molecular-beam epitaxy on sapphire and SiC

Zuzanna Liliental-Weber, Hyunchul Sohn, Nathan Newman, Jack Washburn

Research output: Contribution to journalArticle

66 Citations (Scopus)

Abstract

Transmission electron microscopy was used for the characterization of GaN epitaxial layers grown by molecular-beam epitaxy on two different substrates: sapphire (Al2O3) and 6H-SiC. GaN layers grown on both substrates crystallize with the wurtzite structure. Despite the very different lattice mismatch associated with their two substrates, similar types of defects were formed in the GaN layer; only their density differed. In addition to small-angle subgrain boundaries two other types of defects were seen in cross-sectioned samples: defects parallel to the growth surface. The parallel defects were with a width of about 8-10 nm perpendicular to the growth surface. The parallel defects were identified as stacking faults leading to a local fcc atom arrangement in the layer and are believed to be growth defects. The density of these faults decreased with layer thickness. However, the density of the vertical microtwins remained constant through the layer. Slight local lattice twists between the microtwins and surrounding areas or differences of stoichiometry are suggested as an explanation for the observed contrast of the high-resolution images.

Original languageEnglish
Pages (from-to)1578-1581
Number of pages4
JournalJournal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures
Volume13
Issue number4
DOIs
Publication statusPublished - 1995 Jul 1

Fingerprint

Molecular beam epitaxy
Sapphire
Electron microscopy
electron microscopy
sapphire
molecular beam epitaxy
Defects
defects
Substrates
Lattice mismatch
Epitaxial layers
Stacking faults
Image resolution
crystal defects
Stoichiometry
wurtzite
stoichiometry
Transmission electron microscopy
Atoms
transmission electron microscopy

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Electrical and Electronic Engineering

Cite this

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title = "Electron microscopy characterization of GaN films grown by molecular-beam epitaxy on sapphire and SiC",
abstract = "Transmission electron microscopy was used for the characterization of GaN epitaxial layers grown by molecular-beam epitaxy on two different substrates: sapphire (Al2O3) and 6H-SiC. GaN layers grown on both substrates crystallize with the wurtzite structure. Despite the very different lattice mismatch associated with their two substrates, similar types of defects were formed in the GaN layer; only their density differed. In addition to small-angle subgrain boundaries two other types of defects were seen in cross-sectioned samples: defects parallel to the growth surface. The parallel defects were with a width of about 8-10 nm perpendicular to the growth surface. The parallel defects were identified as stacking faults leading to a local fcc atom arrangement in the layer and are believed to be growth defects. The density of these faults decreased with layer thickness. However, the density of the vertical microtwins remained constant through the layer. Slight local lattice twists between the microtwins and surrounding areas or differences of stoichiometry are suggested as an explanation for the observed contrast of the high-resolution images.",
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Electron microscopy characterization of GaN films grown by molecular-beam epitaxy on sapphire and SiC. / Liliental-Weber, Zuzanna; Sohn, Hyunchul; Newman, Nathan; Washburn, Jack.

In: Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures, Vol. 13, No. 4, 01.07.1995, p. 1578-1581.

Research output: Contribution to journalArticle

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AU - Sohn, Hyunchul

AU - Newman, Nathan

AU - Washburn, Jack

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N2 - Transmission electron microscopy was used for the characterization of GaN epitaxial layers grown by molecular-beam epitaxy on two different substrates: sapphire (Al2O3) and 6H-SiC. GaN layers grown on both substrates crystallize with the wurtzite structure. Despite the very different lattice mismatch associated with their two substrates, similar types of defects were formed in the GaN layer; only their density differed. In addition to small-angle subgrain boundaries two other types of defects were seen in cross-sectioned samples: defects parallel to the growth surface. The parallel defects were with a width of about 8-10 nm perpendicular to the growth surface. The parallel defects were identified as stacking faults leading to a local fcc atom arrangement in the layer and are believed to be growth defects. The density of these faults decreased with layer thickness. However, the density of the vertical microtwins remained constant through the layer. Slight local lattice twists between the microtwins and surrounding areas or differences of stoichiometry are suggested as an explanation for the observed contrast of the high-resolution images.

AB - Transmission electron microscopy was used for the characterization of GaN epitaxial layers grown by molecular-beam epitaxy on two different substrates: sapphire (Al2O3) and 6H-SiC. GaN layers grown on both substrates crystallize with the wurtzite structure. Despite the very different lattice mismatch associated with their two substrates, similar types of defects were formed in the GaN layer; only their density differed. In addition to small-angle subgrain boundaries two other types of defects were seen in cross-sectioned samples: defects parallel to the growth surface. The parallel defects were with a width of about 8-10 nm perpendicular to the growth surface. The parallel defects were identified as stacking faults leading to a local fcc atom arrangement in the layer and are believed to be growth defects. The density of these faults decreased with layer thickness. However, the density of the vertical microtwins remained constant through the layer. Slight local lattice twists between the microtwins and surrounding areas or differences of stoichiometry are suggested as an explanation for the observed contrast of the high-resolution images.

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