Short CV/Education and training

  • 1979 – 1983
    Department of Natural Philosophy, Glasgow University, BSc Honours: Natural Philosophy

  • 1983 – 1984
    Department of Physics, University of St Andrews, MSc: Investigation of the interaction of 'hot' electrons with shallow donor impurity atoms in n-GaAs

Selected publications

  • G. Naresh-Kumar, A. Vilalta-Clemente, S. Pandey, D. Skuridina, H. Behmenburg, P. Gamarra, G. Patriarche, I. Vickridge, M. A. di Forte-Poisson, P. Vogt, M. Kneissl, M. Morales, P. Ruterana, A. Cavallini, D. Cavalcoli, C. Giesen, M. Heuken and C. Trager-Cowan. “Multicharacterization approach for studying InAl(Ga)N/Al(Ga)N/GaN heterostructures for high electron mobility transistors” AIP Advances 4, 127101 (2014).

  • G. Naresh-Kumar, J. Bruckbauer, P. R. Edwards, S. Kraeusel, B. Hourahine, R. W. Martin, M. J. Kappers, M. A. Moram, S. Lovelock, R. A. Oliver, C. J. Humphreys, and C. Trager-Cowan,“Coincident Electron Channeling and Cathodoluminescence Studies of Threading Dislocations in GaN”, Microsc. Microanal. 20, 55 (2014).

  • S. Nagarajan, O. Svensk, M. Ali, G. Naresh-Kumar, C. Trager-Cowan, S. Suihkonen, M. Sopanen, and H. Lipsanen,“Stress distribution of GaN layer grown on micro-pillar patterned GaN templates”, Appl Phys Lett. 103, 012102 (2013).

  • G. Naresh-Kumar, C. Mauder, K. R. Wang, S. Kraeusel, J. Bruckbauer, P. R. Edwards, B. Hourahine, H. Kalisch, A. Vescan, C. Giesen, M. Heuken, A. Trampert, A. P. Day, and C. Trager-Cowan,“Electron channeling contrast imaging studies of nonpolar nitrides using a scanning electron microscope”, Appl Phys Lett. 102, 142103 (2013).

  • G. Naresh-Kumar, B. Hourahine, P. R. Edwards, A. P. Day A. Winkelmann, A. J. Wilkinson P. J. Parbrook, G. England and C Trager-Cowan “Rapid nondestructive analysis of threading dislocations in wurtzite materials using the scanning electron microscope”, Phys. Rev. Lett. 108, 135503 (2012)

  • C. Trager-Cowan, F. Sweeney, P. W. Trimby, A. P. Day, A. Gholinia, N.-H. Schmidt, P. J. Parbrook, A. J. Wilkinson and I. M. Watson, “Electron backscatter diffraction and electron channelling contrast imaging of tilt and dislocations in nitride thin films”, Physical Review B 75, 085301 (2007)

  • A. Winkelmann, C. Trager-Cowan, F. Sweeney, A. Day and P. J. Parbrook, “Many-beam dynamical simulation of electron backscatter diffraction patterns”, Ultramicroscopy 107, 414 (2007)



Complete list of publications

Selected projects

  • Our research is driven by the need for a rapid, non-destructive technique to reveal and analyse defects in crystalline materials, in particular in nitride semiconductor thin films.

    III-nitride materials are presently the basis of a fast-growing, multi-billion dollar solid-state lighting industry and commercial AlGaN/GaN electronic devices are now in use in cell phone base stations, satellite communication systems and cable television networks. However, the ultimate performance of these nitride semiconductor based light emitters and electronic devices is limited by extended defects such as threading dislocations (TDs), partial dislocations (PDs) and stacking faults (SFs). If we want to develop LEDs to be an effective replacement for the light bulb, or have sufficient power to purify water or develop efficient power electronics for electric vehicles, we need to eliminate these defects as they act as scattering centres for light and charge carriers and give rise to nonradiative recombination and to leakage currents, severely limiting device performance. The first step to this goal is the detection of these defects – I am leading a team exploiting electron channeling contrast imaging (ECCI) in a field emission scanning electron microscope to rapidly detect and analyze TDs, PDs and SFs, with negligible sample preparation.

    In ECCI vertical threading dislocations are revealed as spots with black-white (B-W) contrast. We have developed a procedure which exploits the change observed in the direction of this B-W contrast for screw, edge and mixed dislocations, on comparing two electron channeling contrast images acquired from symmetrically equivalent crystal planes. This enables us to unambiguously differentiate between screw, edge and mixed dislocations. We have also demonstrated the use of ECCI to reveal and characterize basal plane stacking faults in nonpolar nitride semiconductors. Comparing electron channeling contrast images with cathodoluminescence hyperspectral data from exactly the same micron-scale region of a sample is allowing us to investigate the influence of defects on the light emission from nitride semiconductors. In addition to our experimental work we have also been developing image analysis and statistical analysis tools to help extract information from the electron channelling contrast images. Finally, in collaboration with the Universities of Glasgow and the National Physical laboratory, we are developing new direct electron imaging detectors for the ECCI technique and its sister technique of electron backscatter diffraction.

Membership in scientific bodies/juries

  • Fellow of the Institute of Physics (UK)

  • Fellow of the Royal Microscopical Society (UK)

  • Fellow of the Royal Society of Edinburgh

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