Properties of Defective Regions Observed by Photoluminescence Imaging for GaN-Based Light-Emitting Diode Epi-Wafers

  • Kim, Jongseok ;
  • Kim, HyungTae ;
  • Kim, Seungtaek ;
  • Jeong, Hoon ;
  • Cho, In-Sung ;
  • Noh, Min Soo ;
  • Jung, Hyundon ;
  • Jin, Kyung Chan
  • Received : 2015.09.09
  • Accepted : 2015.11.03
  • Published : 2015.12.25


A photoluminescence (PL) imaging method using a vision camera was employed to inspect InGaN/GaN quantum-well light-emitting diode (LED) epi-wafers. The PL image revealed dark spot defective regions (DSDRs) as well as a spatial map of integrated PL intensity of the epi-wafer. The Shockley-Read-Hall (SRH) nonradiative recombination coefficient increased with the size of the DSDRs. The high nonradiative recombination rates of the DSDRs resulted in degradation of the optical properties of the LED chips fabricated at the defective regions. Abnormal current-voltage characteristics with large forward leakages were also observed for LED chips with DSDRs, which could be due to parallel resistances bypassing the junction and/or tunneling through defects in the active region. It was found that the SRH nonradiative recombination process was dominant in the voltage range where the forward leakage by tunneling was observed. The results indicated that the DSDRs observed by PL imaging of LED epi-wafers were high density SRH nonradiative recombination centers which could affect the optical and electrical properties of the LED chips, and PL imaging can be an inspection method for evaluation of the epi-wafers and estimation of properties of the LED chips before fabrication.


Light-emitting diodes;Photoluminescence;Imaging;Optical inspection


  1. E. F. Schubert and J. K. Kim, “Solid-state light sources getting smart,” Science 308, 1274-1278 (2005).
  2. G. Tamulaitis, J. Mickevičius, D. Dobrovolskas, E. Kuokštis, M. Shur, M. Shatalov, J. Yang, and R. Gaska, “Spatially-resolved photoluminescence study of high indium content InGaN LED structures,” Phys. Status Solidi C 7, 1869-1871 (2010).
  3. Y.-S. Choi, J.-H. Park, S.-S. Kim, H.-J. Song, S.-H. Lee, J.-J. Jung, and B.-T. Lee, “Effects of dislocations on the luminescence of GaN/InGaN multi-quantum-well light-emitting-diode layers,” Mater. Lett. 58, 2614-2617 (2004).
  4. A. Kaneta, K. Okamoto, Y. Kawakami, S. Fujita, G. Marutsuki, Y. Narukawa, and T. Mukai, “Spatial and temporal luminescence dynamics in an InxGa1-xN single quantum well probed by near-field optical microscopy,” Appl. Phys. Lett. 81, 4353-4355 (2002).
  5. G. Livescu, M. Angell, J. Filipe, and W. H. Knox, "A real-time photoluminescence imaging system," J. Electron. Mater. 19, 937-941 (1990).
  6. H.-T. Kim, J. Kim, S. Kim, H.-K. Yuh, D.-H. Kim, D.-H. Ahn, and D.-S. Shin, “A dual side electroluminescence measurement system for LED wafer manufacturing,” Recent Patents on Signal Proc. 3, 49-55 (2013).
  7. Y. H. Aliyu, D. V. Morgan, and H. Thomas, “A luminescence mapping technique for rapid evaluation of visible-lightemitting materials used in semiconductor light-emitting diodes,” Meas. Sci. Technol. 8, 437-440 (1997).
  8. C. J. Raymond and Z. Li, “Photoluminescence metrology for LED characterization in high volume manufacturing,” Proc. SPIE 8681, 86810P (2013).
  9. S. Nakamura and M. R. Krames, “History of gallium-nitride based light-emitting diodes for illumination,” Proc. IEEE 101, 2211-2220 (2013).
  10. M. Mandurrino, G. Verzellesi, M. Goano, M. Vallone, F. Bertazzi, G. Ghione, M. Meneghini, G. Meneghesso, and E. Zanoni, “Physics-based modeling and experimental implications of trap-assisted tunneling in InGaN/GaN light-emitting diodes,” Phys. Status Solidi A 212, 947-953 (2015).
  11. X. A. Cao, J. M. Teetsov, M. P. D’Evelyn, D. W. Merfeld, and C. H. Yan, “Electrical characteristics of InGaN/GaN light-emitting diodes grown on GaN and sapphire substrates,” Appl. Phys. Lett. 85, 7-9 (2004).
  12. H. Masui, “Diode ideality factor in modern light-emitting diodes,” Semicond. Sci. Technol. 26, 075011 (2011).
  13. E. F. Schubert, Light-Emitting Diodes, 2nd ed. (Cambridge University Press, Cambridge, UK, 2006), Chapter 4.
  14. M. Meneghini, M. la Grassa, S. Vaccari, B. Galler, R. Zeisel, P. Drechsel, B. Hahn, G. Meneghesso, and E. Zanoni, “Characterization of the deep levels responsible for nonradiative recombination in InGaN/GaN light-emitting diodes,” Appl. Phys. Lett. 104, 113505 (2014).
  15. Q. Dai, M. F. Schubert, M. H. Kim, J. K. Kim, E. F. Schubert, D. D. Koleske, M. H. Crawford, S. R. Lee, A. J. Fischer, G. Thaler, and M. A. Banas, “Internal quantum efficiency and nonradiative recombination coefficient of GaInN/GaN multiple quantum wells with different dislocation densities,” Appl. Phys. Lett. 94, 111109 (2009).
  16. J. P. Bergman, H. Jakobsson, L. Storasta, F. H. C. Carlsson, B. Magnusson, S. Sridhara, G. Pozina, H. Lendenmann, and E. Janzén, “Characterization and defects in silicon carbide,” Mater. Sci. Forum 389-393, 9-14 (2002).
  17. T. Trupke, R. A. Bardos, M. C. Schubert, and W. Warta, “Photoluminescence imaging of silicon wafers,” Appl. Phys. Lett. 89, 044107 (2006).
  18. I. Mártil, E. Redondo, and A. Ojeda, “Influence of defects on the electrical and optical characteristics of blue light-emitting diodes based on III-V nitrides,” J. Appl. Phys. 81, 2442-2444 (1997).
  19. I.-G. Choi, D.-P. Han, J. Yun, K. S. Kim, D.-S. Shin, and J.-I. Shim, “Investigation of dominant nonradiative mechanisms as a function of current in InGaN/GaN light-emitting diodes,” Appl. Phys. Express 6, 052105 (2013).
  20. H. Masui, T. Ive, M. C. Schmidt, N. N. Fellows, H. Sato, H. Asamizu, S. Nakamura, and S. P. Denbaars, “Equivalent-circuit analysis for the electroluminescence-efficiency problem of InGaN/GaN light-emitting diodes,” Jpn. J. Appl. Phys. 47, 2112-2118 (2008).
  21. M. Binder, B. Galler, M. Furitsch, J. Off, J. Wagner, R. Zeisel, and S. Katz, “Investigations on correlation between I-V characteristics and internal quantum efficiency of blue (AlGaIn)N light-emitting diodes,” Appl. Phys. Lett. 103, 221110 (2013).
  22. D. Yan, H. Lu, D. Chen, R. Zhang, and Y. Zheng, “Forward tunneling current in GaN-based blue light-emitting diodes,” Appl. Phys. Lett. 96, 083504 (2010).
  23. K. Sakowski, L. Marcinkowski, S. Krukowski, S. Grzanka, and E. Litwin-Staszewska, “Simulation of trap-assisted tunneling effect on characteristics of gallium nitride diodes,” J. Appl. Phys. 111, 123115 (2012).
  24. M. Auf der Maur, B. Galler, I. Pietzonka, M. Strassburg, H. Lugauer, and A. Di Carlo, “Trap-assisted tunneling in InGaN/GaN single-quantum-well light-emitting diodes,” Appl. Phys. Lett. 105, 133504 (2014).
  25. K.-S. Kim, D.-P. Han, H.-S. Kim, and J.-I. Shim, “Analysis of dominant carrier recombination mechanisms depending on injection current in InGaN green light emitting diodes,” Appl. Phys. Lett. 104, 091110 (2014).
  26. M. Meneghini, L.-R. Trevisanello, G. Meneghesso, and E. Zanoni, “A review on the reliability of GaN-based LEDs,” IEEE Trans. Device Mater. Reliab. 8, 323-331 (2008).
  27. X. A. Cao, E. B. Stokes, P. M. Sandvik, S. F. LeBoeuf, J. Kretchmer, and D. Walker, “Diffusion and tunneling currents in GaN/InGaN multiple quantum well light-emitting diodes,” IEEE Electron Device Lett. 23, 535-537 (2002).