Influence of free-standing GaN substrate on ultraviolet light-emittingdiodes by atmospheric-pressure metal-organic chemical vapor deposition

C. Y. Shieh, Z. Y. Li, C. H. Chiu, P. M. Tu, Hao-Chung Kuo, G. C. Chi

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Scopus citations

Abstract

We reported the influence of free-standing (FS) GaN substrate on ultraviolet light-emitting-diodes (UV LEDs) by atmospheric-pressure metal-organic chemical vapor deposition (APMOCVD). The Raman spectrum shows the in-plane compressive stress of the GaN epitaxial structures grown on FS GaN substrate. Besides, the Raman spectrum reveals the relation between the crystal quality and the carrier localization degree in multi-quantum wells (MQWs). High resolution X-ray diffraction (HRXRD) analysis results show that the In0 025Ga0 975N/Al0 08Ga0 92N MQWs grown on FS GaN substrate has higher indium mole fraction than sapphire at the same growth conditions. The higher indium incorporation is corresponding with the red-shift 6 nm (387 nm) of the room temperature photoluminescence (PL) peak. The full widths at half maximum (FWHM) of omega-scan rocking curve in (002) and (102) reflectance on FS GaN substrate (83 arcsec and 77 arcsec) are narrower than UV LEDs grown on sapphire (288 arcsec and 446 arcsec). This superior quality may attribute to homoepitaxial growth structure and better strain relaxation in the FS GaN substrate. An anomalous temperature behavior of PL in UV LEDs designated as an S-shaped peak position dependence and W-shaped linewidth dependence indicate that exciton/carrier motion occurs via photon-assisted tunneling through localized states, what results in incomplete thermalization of localized excitons at low temperature. The Gaussian broadening parameters of carrier localization is about 16.98 meV from the temperature dependent photoluminescence (TDPL) measurement. The saturation temperature from the TDPL linewidth of UV LEDs on FS GaN substrate at about 175 K represents a crossover from a nonthermalized to thermalized energy distribution of excitons.

Original languageEnglish
Title of host publicationGallium Nitride Materials and Devices VIII
DOIs
StatePublished - 12 Jun 2013
EventSPIE Symposium on Gallium Nitride Materials and Devices VIII - San Francisco, CA, United States
Duration: 4 Feb 20137 Feb 2013

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
Volume8625
ISSN (Print)0277-786X

Conference

ConferenceSPIE Symposium on Gallium Nitride Materials and Devices VIII
CountryUnited States
CitySan Francisco, CA
Period4/02/137/02/13

Keywords

  • APMOCVD
  • FS GaN substrate
  • HRXRD
  • InGaN/AlGaN MQWs
  • PL
  • Raman
  • UV LEDs

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    Shieh, C. Y., Li, Z. Y., Chiu, C. H., Tu, P. M., Kuo, H-C., & Chi, G. C. (2013). Influence of free-standing GaN substrate on ultraviolet light-emittingdiodes by atmospheric-pressure metal-organic chemical vapor deposition. In Gallium Nitride Materials and Devices VIII [862525] (Proceedings of SPIE - The International Society for Optical Engineering; Vol. 8625). https://doi.org/10.1117/12.2003673