Diffraction Contrast of Threading Dislocations in GaN 
and 4H-SiC Epitaxial Layers Using Electron Channeling Contrast Imaging

AbstractWe combine two scanning electron microscopy techniques to investigate the influence of dislocations on the light emission from nitride semiconductors. Combining electron channeling contrast imaging and cathodoluminescence imaging enables both the structural and luminescence properties of a sample to be investigated without structural damage to the sample. The electron channeling contrast image is very sensitive to distortions of the crystal lattice, resulting in individual threading dislocations appearing as spots with black–white contrast. Dislocations giving rise to nonradiative recombination are observed as black spots in the cathodoluminescence image. Comparison of the images from exactly the same micron-scale region of a sample demonstrates a one-to-one correlation between the presence of single threading dislocations and resolved dark spots in the cathodoluminescence image. In addition, we have also obtained an atomic force microscopy image from the same region of the sample, which confirms that both pure edge dislocations and those with a screw component (i.e., screw and mixed dislocations) act as nonradiative recombination centers for the Si-doped c-plane GaN thin film investigated.

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Using Multiple Contrast Mechanisms via Forescatter Electron Channeling Contrast Imaging to Resolve the Burgers Vector of GaN Threading Dislocations

Microscopy and Microanalysis ◽

10.1017/s1431927609094562 ◽

2009 ◽

Vol 15 (S2) ◽

pp. 674-675

Author(s):

YN Picard ◽

ME Twigg ◽

JD Caldwell ◽

CR Eddy Jr. ◽

MA Mastro ◽

...

Keyword(s):

Threading Dislocations ◽

Contrast Imaging ◽

Burgers Vector ◽

Electron Channeling ◽

Contrast Mechanisms

Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009

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Electron channeling contrast imaging of atomic steps and threading dislocations in 4H-SiC

Applied Physics Letters ◽

10.1063/1.2746075 ◽

2007 ◽

Vol 90 (23) ◽

pp. 234101 ◽

Cited By ~ 38

Author(s):

Y. N. Picard ◽

M. E. Twigg ◽

J. D. Caldwell ◽

C. R. Eddy ◽

P. G. Neudeck ◽

...

Keyword(s):

Threading Dislocations ◽

Contrast Imaging ◽

Atomic Steps ◽

Electron Channeling

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Simulation of Forescattered Electron Channeling Contrast Imaging of Threading Dislocations Penetrating SiC Surfaces

MRS Proceedings ◽

10.1557/proc-1068-c03-20 ◽

2008 ◽

Vol 1068 ◽

Author(s):

Mark E. Twigg ◽

Yoosuf N. Picard ◽

Joshua D. Caldwell ◽

Charles R. Eddy ◽

Philip G. Neudeck ◽

...

Keyword(s):

Primary Source ◽

Threading Dislocations ◽

Contrast Imaging ◽

Screw Dislocations ◽

Burgers Vector ◽

Image Intensity ◽

Electron Channeling ◽

Kikuchi Line ◽

Simulated Images

ABSTRACTThe interpretation of ECCI images in the forescattered geometry presents a more complex diffraction configuration than that encountered in the backscattered geometry. Determining the Kikuchi line that is the primary source of image intensity often requires more than simple inspection of the electron-channeling pattern. This problem can be addressed, however, by comparing recorded ECCI images of threading screw dislocations in 4H-SiC with simulated images. An ECCI image of this dislocation is found to give the orientation of the dominant Kikuchi line, greatly simplifying the determination of the diffraction simulation. In addition, computed images of threading screw dislocations in 4H-SiC were found to exhibit channeling contrast essentially identical to that obtained experimentally by ECCI and allowing determination of the dislocation Burgers vector.

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Nondestructive analysis of threading dislocations in GaN by electron channeling contrast imaging

Applied Physics Letters ◽

10.1063/1.2777151 ◽

2007 ◽

Vol 91 (9) ◽

pp. 094106 ◽

Cited By ~ 39

Author(s):

Y. N. Picard ◽

J. D. Caldwell ◽

M. E. Twigg ◽

C. R. Eddy ◽

M. A. Mastro ◽

...

Keyword(s):

Threading Dislocations ◽

Nondestructive Analysis ◽

Contrast Imaging ◽

Electron Channeling

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Strain analysis with nanometer resolution using a conventional transmission electron microsopy technique: electron diffraction contrast imaging revisited

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100137215 ◽

1995 ◽

Vol 53 ◽

pp. 168-169

Author(s):

Koenraad G F Janssens ◽

Omer Van der Biest ◽

Jan Vanhellemont ◽

Herman E Maes ◽

Robert Hull

Keyword(s):

Electron Diffraction ◽

Strain Field ◽

Elastic Strain ◽

Strain Analysis ◽

Local Strain ◽

Contrast Imaging ◽

Strain Characterization ◽

Physical Mechanisms ◽

Diffraction Contrast ◽

Transmission Electron

There is a growing need for elastic strain characterization techniques with submicrometer resolution in several engineering technologies. In advanced material science and engineering the quantitative knowledge of elastic strain, e.g. at small particles or fibers in reinforced composite materials, can lead to a better understanding of the underlying physical mechanisms and thus to an optimization of material production processes. In advanced semiconductor processing and technology, the current size of micro-electronic devices requires an increasing effort in the analysis and characterization of localized strain. More than 30 years have passed since electron diffraction contrast imaging (EDCI) was used for the first time to analyse the local strain field in and around small coherent precipitates1. In later stages the same technique was used to identify straight dislocations by simulating the EDCI contrast resulting from the strain field of a dislocation and comparing it with experimental observations. Since then the technique was developed further by a small number of researchers, most of whom programmed their own dedicated algorithms to solve the problem of EDCI image simulation for the particular problem they were studying at the time.

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