Poster Presentation 24th Australian Conference on Microscopy and Microanalysis 2016

Insight into GaN-based blue VLED using SEM-TKD and TEM (#230)

Mansoor Khan 1 , Rongkun Zheng 1
  1. School of Physics, The University of Sydney, 2006, NSW, Australia

In III-Nitride semiconductor technology, Gallium Nitride (GaN)-based vertical light emitting diode (VLED) possesses superior light emission property compared to its competitive lateral LED (LLED) architecture; such as large light-emitting area by using one electrode, mitigation of current-crowing problem, light-extraction efficiency by roughening the n-GaN surface and better reflection of downward-absorbing light by placing reflection (mirror) layer on the top of substrate [1-3].

The efficacy of the LED relies on many factors, ranges from electrical efficiency to internal quantum efficiency (IQE) to spectral efficiency. Nevertheless, the IQE has been main criteria for the LED performance and is approaching 50-60% in today’s LED market products, but projecting varying levels of improvement across these aspects still need to be explored.

In this report, GaN-based blue VLED incorporating compound epitaxial films grown on a metal-alloy substrate will be analysed under the powerful microscopic tools of Zeiss Ultra plus SEM-EDS and JEOL 2200FS/3000F. Combined SEM-EDS/EBSD, SEM-TKD [4] and STEM analysis helps us to investigate the chemical composition (quantitative and qualitative), epitaxial layers- interface boundaries, grain structures, textures, segregation boundaries, and phases exists in between n-GaN multiple quantum wells (MQWs) and substrate layer. Further, in order to pursue challenging factor of IQE, key reflection layer (below p-GaN) and metal-alloy substrate junctions will be scrutinized.

In this context, motivation is to highlight the GaN-based blue VLED in terms of its efficiency. Particularly, focus of the research is to present a competitive analysis performed by SEM+TEM techniques on the fabricated VLED product. Further, the goal is to figure out possible solutions to design efficient and low-cost VLED technology.

Acknowledgement
The authors acknowledge the facilities, scientific and technical assistance of the Australian Microscopy & Microanalysis Research Facility (AMMRF) provided by Australian Centre for Microscopy & Microanalysis (ACMM) at the University of Sydney.

References

  1. S. Pimputkar, J. S. Speck, S. P. DenBaars, and S. Nakamura, “Prospects for LED lighting”, Nat. Photon., vol. 3, no. 4, pp. 180–182, Apr. 2009.
  2. R.Quay, Gallium Nitride Electronics (Springer Series in Material Science, Germany, 98, 2008.
  3. B. Hahn, B.Galler and K.Engl, “Development of high-efficiency and high-power vertical light emitting diodes”, The Japan Soc. of Appl. Phys., vol. 53, no. 10, Sep. 2014.
  4. P.W. Trimby, “Orientation mapping of nanostructured materials using transmission Kikuchi diffraction in the scanning electron microscope”, Ultramicroscopy, vol.120, pp. 16-24, Sep. 2012.