Analysis of composition fluctuations on an atomic scale in Al0.25Ga0.75N by high-resolution transmission electron microscopy

B. Neubauer; A. Rosenauer; D. Gerthsen; O. Ambacher; M. Stutzmann

doi:10.1063/1.122041

Analysis of composition fluctuations on an atomic scale in Al_0.25Ga_0.75N by high-resolution transmission electron microscopy

B. Neubauer, A. Rosenauer, D. Gerthsen, O. Ambacher, M. Stutzmann

TUM Emeriti of Excellence

Research output: Contribution to journal › Article › peer-review

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Abstract

Composition fluctuations in the Al_0.25Ga_0.75N layer of an AlGaN/GaN transistor structure grown by plasma induced molecular beam epitaxy on Al₂O₃(0001) at a growth temperature of 870 °C were studied by digital analysis of lattice images (DALI) of high-resolution transmission electron microscopy (HRTEM) cross-section images. DALI exploits the linear dependence of the lattice parameters on the Al content by applying Vegard's law. Detecting the distances between intensity maxima positions in the micrograph which can be considered as a fingerprint of the local lattice parameters quantitatively derives composition profiles on an atomic scale. In the HRTEM cross-section image different areas were observed in the Al_0.25Ga_0.75N layer with either homogeneous or "striped" contrast. In the striped areas the analyses indicate a strong periodic decomposition with a period of 1 nm consisting of 1 ML Al_0.8Ga_0.2N and about 3 ML Al_0.07Ga_0.93N. The regions with homogeneous contrast do not exhibit significant composition fluctuations.

Original language	English
Pages (from-to)	930-932
Number of pages	3
Journal	Applied Physics Letters
Volume	73
Issue number	7
DOIs	https://doi.org/10.1063/1.122041
State	Published - 1998

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title = "Analysis of composition fluctuations on an atomic scale in Al0.25Ga0.75N by high-resolution transmission electron microscopy",

abstract = "Composition fluctuations in the Al0.25Ga0.75N layer of an AlGaN/GaN transistor structure grown by plasma induced molecular beam epitaxy on Al2O3(0001) at a growth temperature of 870 °C were studied by digital analysis of lattice images (DALI) of high-resolution transmission electron microscopy (HRTEM) cross-section images. DALI exploits the linear dependence of the lattice parameters on the Al content by applying Vegard's law. Detecting the distances between intensity maxima positions in the micrograph which can be considered as a fingerprint of the local lattice parameters quantitatively derives composition profiles on an atomic scale. In the HRTEM cross-section image different areas were observed in the Al0.25Ga0.75N layer with either homogeneous or {"}striped{"} contrast. In the striped areas the analyses indicate a strong periodic decomposition with a period of 1 nm consisting of 1 ML Al0.8Ga0.2N and about 3 ML Al0.07Ga0.93N. The regions with homogeneous contrast do not exhibit significant composition fluctuations.",

author = "B. Neubauer and A. Rosenauer and D. Gerthsen and O. Ambacher and M. Stutzmann",

year = "1998",

doi = "10.1063/1.122041",

language = "English",

volume = "73",

pages = "930--932",

journal = "Applied Physics Letters",

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publisher = "American Institute of Physics",

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T1 - Analysis of composition fluctuations on an atomic scale in Al0.25Ga0.75N by high-resolution transmission electron microscopy

AU - Neubauer, B.

AU - Rosenauer, A.

AU - Gerthsen, D.

AU - Ambacher, O.

AU - Stutzmann, M.

PY - 1998

Y1 - 1998

N2 - Composition fluctuations in the Al0.25Ga0.75N layer of an AlGaN/GaN transistor structure grown by plasma induced molecular beam epitaxy on Al2O3(0001) at a growth temperature of 870 °C were studied by digital analysis of lattice images (DALI) of high-resolution transmission electron microscopy (HRTEM) cross-section images. DALI exploits the linear dependence of the lattice parameters on the Al content by applying Vegard's law. Detecting the distances between intensity maxima positions in the micrograph which can be considered as a fingerprint of the local lattice parameters quantitatively derives composition profiles on an atomic scale. In the HRTEM cross-section image different areas were observed in the Al0.25Ga0.75N layer with either homogeneous or "striped" contrast. In the striped areas the analyses indicate a strong periodic decomposition with a period of 1 nm consisting of 1 ML Al0.8Ga0.2N and about 3 ML Al0.07Ga0.93N. The regions with homogeneous contrast do not exhibit significant composition fluctuations.

AB - Composition fluctuations in the Al0.25Ga0.75N layer of an AlGaN/GaN transistor structure grown by plasma induced molecular beam epitaxy on Al2O3(0001) at a growth temperature of 870 °C were studied by digital analysis of lattice images (DALI) of high-resolution transmission electron microscopy (HRTEM) cross-section images. DALI exploits the linear dependence of the lattice parameters on the Al content by applying Vegard's law. Detecting the distances between intensity maxima positions in the micrograph which can be considered as a fingerprint of the local lattice parameters quantitatively derives composition profiles on an atomic scale. In the HRTEM cross-section image different areas were observed in the Al0.25Ga0.75N layer with either homogeneous or "striped" contrast. In the striped areas the analyses indicate a strong periodic decomposition with a period of 1 nm consisting of 1 ML Al0.8Ga0.2N and about 3 ML Al0.07Ga0.93N. The regions with homogeneous contrast do not exhibit significant composition fluctuations.

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U2 - 10.1063/1.122041

DO - 10.1063/1.122041

M3 - Article

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SN - 0003-6951

VL - 73

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EP - 932

JO - Applied Physics Letters

JF - Applied Physics Letters

IS - 7

ER -

Analysis of composition fluctuations on an atomic scale in Al_0.25Ga_0.75N by high-resolution transmission electron microscopy

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