Hostname: page-component-78c5997874-fbnjt Total loading time: 0 Render date: 2024-11-10T20:02:44.461Z Has data issue: false hasContentIssue false
  • English
  • Français

A TEM Investigation of Crack Reduction in AlGaN/GaN Heterostructures Using an AlN Interlayer

Published online by Cambridge University Press:  01 February 2011

Peter David Cherns ,
Clifford McAleese ,
Jonathan S Barnard ,
Menno J Kappers  and
Colin J Humphreys
Peter David Cherns
Affiliation:
pc291@cam.ac.uk, University of Cambridge, Materials Science and Metallurgy, Pembroke Street, Cambridge, N/A, CB2 3QZ, United Kingdom
Clifford McAleese
Affiliation:
cm254@cam.ac.uk, University of Cambridge, Materials Science and Metallurgy, United Kingdom
Jonathan S Barnard
Affiliation:
jsb43@cam.ac.uk, University of Cambridge, Materials Science and Metallurgy, United Kingdom
Menno J Kappers
Affiliation:
mjk30@cam.ac.uk, University of Cambridge, Materials Science and Metallurgy, United Kingdom
Colin J Humphreys
Affiliation:
colin.humphreys@msm.cam.ac.uk, University of Cambridge, Materials Science and Metallurgy, United Kingdom
Get access

Abstract

A series of Al0.47Ga0.53N/GaN heterostructures with different AlN interlayer thicknesses ranging from 1nm to 50nm has been examined. It was found that when the interlayer thickness is greater than ∼5nm, it becomes possible to grow 250nm of Al0.47Ga0.53N without cracking. The interlayers are then believed to be sufficiently relaxed to place the AlGaN under compressive strain. The mechanisms for this relaxation have been studied using high angle annular dark field (HAADF) imaging, conventional transmission electron microscopy (TEM), energy-filtered TEM (EFTEM) and electron energy loss spectroscopy (EELS). It is found that relaxation takes place through both the small-scale cracking of the interlayer and the generation of misfit dislocations at the GaN/AlN interface. EELS and EFTEM have been used to probe the Al and Ga content of both the material filling the interlayer cracks, and the interlayer itself. This chemical analysis suggests Ga-rich AlGaN areas inside the interlayer cracks and also significant compositional variations in defect-free interlayer regions. It is observed that relaxation by the generation of misfit dislocations results in an increase in the threading dislocation density of the AlGaN layer, in part due to the bending up of misfit dislocations at crack walls.

Keywords

III-Vtransmission electron microscopy (TEM)electron energy loss spectroscopy (EELS)
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 892 , 2005 , 0892-FF27-12
Copyright
Copyright © Materials Research Society 2006

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

1. Han, J., Crawford, M. H., Shul, R. J., Hearne, S. J., Chason, E., Figiel, J. J., Banas, M., MRS Internet J. Nitride Semicond. Res. 4S1, G7.7 (1999).Google Scholar
2. Amano, H., Iwaya, M., Hayashi, N., Kashima, T., Katsuragawa, M., Takeuchi, T., Wetzel, C. and Akasaki, I., MRS Internet J. Nitride Semicond. Res. 4S1, G10.1 (1999).Google Scholar
3. McAleese, C., Kappers, M. J., Rayment, F. D. G., Cherns, P. and Humphreys, C. J., Journal of Crystal Growth 272, 475 (2004).CrossRefGoogle Scholar
4. Han, J., Waldrip, K. E., Lee, S. R., Figiel, J. J., Hearne, S. J., Peterson, G. A. and Myers, S. M., Appl Phys Lett 78, 67 (2001).CrossRefGoogle Scholar
5. Egerton, R. F., Electron Energy Loss Spectroscopy in the Electron Microscope, 2nd edition (Plenum Press, New York and London, 1996).CrossRefGoogle Scholar
6. Bethoux, J. M., Vennegues, P., Natali, F., Feltin, E., Tottereau, O., Nataf, G., De Mierry, P. and Semond, F., J Appl Phys, 94, 10 (2003).CrossRefGoogle Scholar
7. Sun, Q., Huang, Y., Wang, H., Chen, J., Jin, R. Q., Zhang, S. M., Yang, H., Jiang, D. S. and Jahn, U., Ploog, K. H., Appl Phys Lett, 87, 121914 (2005).CrossRefGoogle Scholar
8. Lafford, T. A., Parbrook, P. J. and Tanner, B. K., Appl Phys Lett, 83, 5434 (2003).CrossRefGoogle Scholar