The effect of free-standing GaN substrate on carrier localization in ultraviolet InGaN light-emitting diodes

Ming Ta Tsai, Chung Ming Chu, Che Hsuan Huang, Yin Hao Wu, Ching Hsueh Chiu, Zhen Yu Li*, Po Min Tu, Wei-I Lee, Hao-Chung Kuo

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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In this study, we have grown 380-nm ultraviolet light-emitting diodes (UV-LEDs) based on InGaN/AlInGaN multiple quantum well (MQW) structures on free-standing GaN (FS-GaN) substrate by atmospheric pressure metal-organic chemical vapor deposition (AP-MOCVD), and investigated the relationship between carrier localization degree and FS-GaN. The micro-Raman shift peak mapping image shows low standard deviation (STD), indicating that the UV-LED epi-wafer of low curvature and MQWs of weak quantum-confined Stark effect (QCSE) were grown. High-resolution X-ray diffraction (HRXRD) analyses demonstrated high-order satellite peaks and clear fringes between them for the UV-LEDs grown on the FS-GaN substrate, from which the interface roughness (IRN) was estimated. The temperature-dependent photoluminescence (PL) measurement confirmed that the UV-LEDs grown on the FS-GaN substrate exhibited better carrier confinement. Besides, the high-resolution transmission electron microscopy (HRTEM) and energy-dispersive spectrometer (EDS) mapping images verified that the UV-LEDs on FS-GaN have fairly uniform distribution of indium and more ordered InGaN/AlInGaN MQW structure. Clearly, the FS-GaN can not only improve the light output power but also reduce the efficiency droop phenomenon at high injection current. Based on the results mentioned above, the FS-GaN can offer UV-LEDs based on InGaN/AlInGaN MQW structures with benefits, such as high crystal quality and small carrier localization degree, compared with the UV-LEDs on sapphire.

Original languageEnglish
JournalNanoscale Research Letters
Issue number1
StatePublished - 1 Dec 2014


  • Carrier confinement
  • External quantum efficiency
  • Homoepitaxially
  • Light-emitting diodes
  • Ultraviolet


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