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Group Meeting

Group Meeting. Topic: Raman and cathodoluminescence study of dislocation in GaN. Reporter: Welson T.H. Sung Date: 2008/3/5. JOURNAL OF APPLIED PHYSICS [VOLUME 92, NUMBER 11] (2002). H. Leia) and H. S. Leipner

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Group Meeting

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  1. Group Meeting Topic: Raman and cathodoluminescence study of dislocation in GaN Reporter: Welson T.H. Sung Date: 2008/3/5

  2. JOURNAL OF APPLIED PHYSICS [VOLUME 92, NUMBER 11] (2002) H. Leia) and H. S. Leipner Center of Materials Science, Hoher Weg 8, Martin Luther University Halle-Wittenberg, D-06120 Halle, Germany J. Schreiber Department of Physics, Friedemann-Bach-Platz 6, Martin Luther University Halle-Wittenberg, D-06108 Halle, Germany J. L. Weyher Experimental Solid Physics III, RIM, University of Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands T. Wosin´ ski Institute of Physics, Polish Academy of Sciences, aleja Lotniko´w 32/46, PL-02668 Warsaw, Poland I. Grzegory High Pressure Research Center, Polish Academy of Sciences, ulica Sokolowska 29/37, PL-01142 Warsaw, Poland

  3. Outline • Motivation • Background info of Sample: GaN • Growth & Etching • Equipment & Method: • Microindenter • Raman&CL • Analyze Spectrum • Conclusion

  4. Motivation • The cause of YL Band (550nm) • Intrinsic defects VGa, dislocation • Impurity( Oxygen, Carbon) • For my further work of analyzing pillar’s spectrum

  5. Background info of Sample: GaN • Growth: N-polar(0001), Wurtzite structure, 250~350oC • Compress: Vickers, 2N, 1~20mins ( Stress induce fresh dislocation ) • Etching: 200~250oC, KOH-NaOH ( Intrinsic dislocation )

  6. Equipment & Method • Micro-Raman: • Laser source: 632.8nm( green), 1um spot, 0.1cm-1 • CL: • 10K (For increase radiation free electron, decrease thermal radiation) • SEM-JSM6400 ( 20kV)

  7. Phonon-Plasmon mode • C6v space group(#183 P6mm) • 8 phonon modes: • E2 X2 (Stress free 567cm-1) • A1(TO) (518cm-1) LOPP-1 • E1(TO) (740cm-1) matrix • B1 X2 • A1(LO) • E1(LO) • Energy transmit between Raman and Lattice vibration

  8. Analyze Spectrum

  9. Analyze Spectrum • Intensity decrease from 1 to 4

  10. Comparision (Near center) • Curves 1 (intensity X1) & 2(intensity X2.3) • C1:LPP combine with A1(TO) • C2: Split: Free electron concentration( close to center), A1(TO) broad. • Curves 1-3 EF peak • Curves3 & 4 EF blue shifting: • Free electron concentration X wrong • Compress stress induce

  11. Comparision (Near center) • Curve 4: Broad,weak of peak E2 (poor order) • Other: • Peak P1 P2: might be phase transformation • (wurtzite => rock-salt structure) • Raman Mapping: (E2 mode peak) compress 1.5GPa Max

  12. Dislocation nonradiative recombination • Intrinsic dislocation etching pit 15um -> larger • -20% compare with Matrix

  13. CL result • Source: 400~1100nm • YL: 550nm • VGa: N-type native acceptor

  14. CL spectrum Curve 1: intrinsic vacancy Curves 2~6: compress induce dislocations and vacancies(blue shift)

  15. Conclusion • GaN brittle to ductile • VGa induce edge dislocation jogging • Intensity of radiation: • recombinative recombination at vacancy • nonradiative recombination at dislocations. • Other possibility

  16. Thank You for Your Attention

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