Generated Carrier Dynamics in V-Pit-Enhanced InGaN/GaN Light-Emitting Diode

Idris A. Ajia, Paul R. Edwards, Yusin Pak, Ermek Belekov, Manuel A. Roldan, Nini Wei, Zhiqiang Liu, Robert W. Martin, Iman S. Roqan*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

58 Scopus citations


We investigate the effects of V-pits on the optical properties of a state-of-the-art, highly efficient, blue InGaN/GaN multi-quantum-well (MQW) light-emitting diode (LED) with a high internal quantum efficiency (IQE) of >80%. The LED is structurally enhanced by incorporating a pre-MQW InGaN strain-relief layer with low InN content and a patterned sapphire substrate. For comparison, a conventional (unenhanced) InGaN/GaN MQW LED (with an IQE of 46%) grown under similar conditions was subjected to the same measurements. Scanning transmission electron microscopy reveals the absence of V-pits in the unenhanced LED, whereas in the enhanced LED, V-pits with {10-11} facets, emerging from threading dislocations (TDs), were prominent. Cathodoluminescence mapping reveals the luminescence properties near the V-pits, showing that the formation of V-pit defects can encourage the growth of defect-neutralizing barriers around TD defect states. The diminished contribution of TDs in the MQWs allows indium-rich localization sites to act as efficient recombination centers. Photoluminescence and time-resolved spectroscopy measurements suggest that the V-pits play a significant role in the generated carrier rate and droop mechanism, showing that the quantum-confined Stark effect is suppressed at low generated carrier density, after which the carrier dynamics and droop are governed by the carrier overflow effect.

Original languageEnglish (US)
Pages (from-to)820-826
Number of pages7
Issue number3
StatePublished - Mar 21 2018


  • InGaN
  • carrier dynamics
  • efficiency droop
  • light-emitting diode
  • time-resolved spectroscopy

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biotechnology
  • Atomic and Molecular Physics, and Optics
  • Electrical and Electronic Engineering


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