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III-V Nitrides

Associate Professor Ewa M. Goldys

April 2001

Gallium nitride and related compounds are emerging electronic material for the next generation electronic and optical devices. Further improvements in material quality are necessary for improved reliability and yield. Amongst the III-V nitrides, gallium nitride has generated most interest due to its application as a blue emitter. Alloys of GaN with indium and aluminum nitrides have also attracted attention as their bandgaps can be selected by compositional control, allowing materials to be produced with optical absorption tailored to ultraviolet wavelength bands.

Our present research program concentrates on the investigations of O and H content in GaN.

Our key experimental methods include cathodoluminescence , Raman and other optical spectroscopies.

Cathodoluminescence is based on the emission of light under intense bombardment using electrons in a specially adapted electron microscope, and it has very significant diagnostic powers including depth-profiling and defect electromigration.

The UV Raman spectroscopy is critical to studies of microstructure and local chemical compositions of nitride films grown at Macquarie University and other collaborating institutions. The excitation wavelength of 325 nm, in close proximity to an electric dipole allowed transition enhances the Raman signal by several orders of magnitude, so sensitive effects may be explored. A variety of film attributes is observed in their effect on the phonon modes. Microstructural information and in-depth resolution through Raman confocal operation is particularly valuable for examination of conventional GaN structures.

Our earlier work concentrated on fundamental studies of defects in GaN and other III-V nitrides by cathodoluminescence (in collaboration with M. Godlewski (Polish Academy of Sciences, and M.R. Phillips (University of Technology, Sydney). These studies help unravel the role of defects for device properties of GaN and they both advance frontiers of scientific inquiry and provide foundation for future technological developments.
In particular

• we have identified principal reasons for film nonuniformities in HVPE growth and identified strategies for their elimination. Further work continues aimed at free-standing films.
• Raman spectroscopy was used to identify the structure of low temperature nitride films and provide information about the crystallite size, a very accurate measure of electronic quality of a semiconductor film, important in thin film characterisation and otherwise accessible only through time-consuming transmission electron microscopy.
• we have discovered in-plane nonuniformities in band-edge emission in MOCVD GaN, while lower energy emissions (yellow band) were found homogeneous.
• the significance of oxygen on the yellow emission was revealed for the first time.

Selected publications

1. Inter-link Between Structural and Optical Properties of GaN and GaN/AlGaN Heterostructures", M. Godlewski and E.M. Goldys to be included in the book ''III-V Nitride Semiconductors: Optical Properties''Hongxing Jiang and M. Omar Manasreh (Co-editors) to be published by Gordon and Breach. (114 pages, http:// www.physics.mq.edu.au/\ ~{goldys/files/review.pdf)
    
2. "Characterisation of the red emission in nominally undoped HVPE GaN", E.M. Goldys, M. Godlewski, T. Paskova, G. Pozina, B. Monemar, MRS Internet Journal of Nitride Research, vol 6, paper 1 (2001).
    
3. "Nonuniform defect distribution in GaN thin films examined by cathodoluminescence", E.M. Goldys and M. Godlewski, Applied Physics A - Materials Science and Processing , 70, 329, (2000)
    
4. "Cathodoluminescence Studies of in-plane and in-depth Properties of GaN Epilayers", M. Godlewski, E.M. Goldys and M.R. Phillips, Journal of Luminescence 87-89, 1155 (2000).
    
5. "Surface morphology of cubic and wurtzite GaN films" E.M. Goldys, M. Godlewski, R. Langer, A. Barski, Applied Surface Science 153, p. 143-149, (2000).
    
6. "Cathodoluminescence Depth-profiling Studies of GaN/AlGaN Quantum Well Structures", M. Godlewski, E.M. Goldys, M.R. Phillips, R. Langer and A. Barski, J. Mat. Research, 15,p. 495-501,(2000).
    
7. rate on the structure of thick GaN layers by HVPE", T. Paskova, E.M. Goldys, R. Yakimova, E.B. Svedberg, A. Henry, and B. Monemar, J. Cryst. Growth, 208 p.18-26(2000).
    
8. "Hydride Vapour Phase Epitaxial GaN Layers Grown on a-plane Sapphire with Different Buffers", T. Paskova, J. Birch, S. Tungasmita, R. Beccard, M. Heuken. E.B. Svedberg, P. Runneson, E.M. Goldys and B. Monemar, physica status solidi a, 176, p. 415-19, (1999).
    
9. "Analysis of the red optical emission in cubic GaN grown by MBE", E.M. Goldys, M. Godlewski, R. Langer, A. Barski, P. Bergman, B. Monemar, Phys. Rev. B, 60, p. 5464-9, (1999).
    
10. T. Paskova, E.M. Goldys, B. Monemar. "Hydride vapour-phase epitaxy growth and cathodoluminescence characterisation of thick GaN films", J. Cryst. Growth, 203, p. 1-11, (1999).
     
11. "Contribution of Free Electron Recombination to the Emission Spectra of GaN grown by HVPE", B. Arnaudov, T. Paskova, E.M. Goldys, R. Yakimova, I.G. Ivanov, S. Evtimova, A. Henry, B. Momenar, J. Appl. Phys. vol 85, (1999) pp.7888-92
     
12. "Direct observation of large-scale nonuniformities in hydride vapor-phase epitaxy-grown gallium nitride by cathodoluminescence",E.M. Goldys, T. Paskova, I.G. Ivanov, B. Arnaudov, B. Monemar, Applied Physics Letters, vol 73, no 24, p. 3583-5, (1998).
     
13. "Influence of the surface morphology on the yellow and "edge" emissions in wurtzite GaN", M. Godlewski, E.M. Goldys, M.R. Phillips, R. Langer and A. Barski, Applied Physics Letters, vol 73, no 25, p. 3686-8, (1998).
     
14. "Morphology and Optical Properties of cubic phase GaN epilayers grown on (001) Si ", M. Godlewski, E.M. Goldys, M.R. Phillips, J.P. Bergman, B. Monemar, R. Langer, A. Barski, MRS Internet Journal of Nitride Semiconductor Research, vol 3, 51 (1998).
     
15. "Mechanisms of red and yellow photoluminescence in wurtzite and cubic GaN" M. Godlewski, T. Suski, I. Grzegory, S. Porowski, R. Langer, A. Barski, J.P. Bergman, B. Monemar, E.M. Goldys, and M.R. Phillips. Acta Physica Polonica, vol 94 no 2 p.326-30 (1998).
     
16. S. Kumar, E.M. Goldys, T.L. Tansley. C.T. Foxon, T.S. Cheng, and S.V. Novikov, "GaN Films Grown by Plasma Assisted Molecular Beam Epitaxy - Morphology and Microstructure Studies", Australian Compound Optoelectronic Materials and Devices Conference (COMAD), Sydney, 12-14 December 1994, p. 189-194.
     
17. "Zirconium Mediated Hydrogen Outdiffusion From p-GaN" E.Kaminska, A. Piotrowska, A. Barcz, M. Zielinski,R.F. Davis, M.D. Bremser, E. Goldys, K. Tomsia, Fall Meeting of the Materials Research Society, Boston, MA, 28 November - 3 December 1999, paper W10.9.1
     
18. "Thermal Stability and Electrical Properties of Ti and Zr-based Nitrides and Borides on GaN (E.Kaminska, A.Piotrowska, A. Barcz, M. Guziewicz, K. Golaszewska, E.Goldys, K.Tomsia, J. Jasinski, J. Kozubowski, E.Dynowska, "Surface and Thin Films" Kazimierz Dolny, 15-18 Sept 1999, Poland to be published in Electron Technology.
     
19. "Photo- and cathodoluminescence investigations of piezoelectric GaN/AlGaN quantum well structures", M.Godlewski, E.M.Goldys, M.R.Phillips, V. Yu Ivanov, R.Langer, A.Barski, 11-th International Semiconducting and Insulating Materials Conference Canberra Australia 3-7 July 2000.
     
20. "Role of localisation effects in GaN and InGaN" (invited talk) M.Godlewski and E.M.Goldys. International Conference Advanced Optical Materials and Devices, ADOM-2, Vilnius, Lithuania, August 16-19, 2000, Proceedings SPIE (in print)
     
21. "Photoluminescence and cathodoluminescence investigations of piezoelectric quantum wells" E. M. Goldys, M. Godlewski, M.R. Phillips, A.A. Toropov, Fall Meeting, Materials Research Society, Boston, MA, USA, 27 November - 1 December 2000.
     
22. "Correlation between Hot Exciton Photoluminescence and Kelvin Probe Force Microscopy in p-type GaN" E.M. Goldys, M. Godlewski, E. Kaminska, A. Piotrowska, G. Koley, M.G. Spencer, L.F. Eastman, 2000 Conference on Optoelectronic and Microelectronic Materials and Devices, Melbourne, Australia, 6-8 December 2000.
     
23. "Cathodoluminescence Study of Nitride Transistor Structures-Characterisation of Native Oxide", E.M. Goldys, T. Paskova, J. Sheely, W. Schaff, L.F. Eastman, 2000 Conference on Optoelectronic and Microelectronic Materials and Devices, Melbourne, Australia, 6-8 December 2000
     
24. "In-plane and in-depths nonuniformities in defect distribution in GaN and InGaN epilayers, M. Godlewski, E.M. Goldys, G. Pozina, B. Monemar, K. Pakula, J.M. Baranowski, P. Prystawko and M. Leszczynski, ICDS21

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