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Impact of fin aspect ratio on enhancement of external quantum efficiency in single AlGaN fin light-emitting diodes pixels



Babak Nikoobakht, Yuqin Zong, Okan Koksal, Amit Agrawal, Christopher B. Montgomery, Jacob Leach, Michael Shur


Previously, we showed within a sub-micron fin shape heterojunction, as current density increases, the non-radiative Auger recombination saturates mediated by the extension of the depletion region into the fin, resulting in a droop-free behavior. In this report, we investigate the dependence of the fin aspect ratio on its external quantum efficiency (EQE) within an array of single n-AlGaN fin/p-GaN heterojunctions. In this architecture, n-metal contact is interfaced with the non-polar side facet of the fin. EQE of single fin pixels is measured as a function of the fin width from 3000 nm to 200 nm. At a fixed current density, as fin width reduces, we systematically observe an increase in the UV excitonic emission of the AlGaN fin and a 7x enhancement in the EQE. We explain this phenomenon by conserving the volume of the carrier depletion region within a fin. As a fin gets thinner, the base area of the depletion volume shrinks, while its height increases within the fin. This geometrical advantage allows a 200 nm wide fin to operate at 1/3 current density of a 3000 nm fin while generating a UV emission with a comparable power of 1 uW. In addition to this enhancement, our results suggest a larger current injection area in fins, and its elongated interface with the substrate further supports its unique performance. These findings are encouraging as they show new parameters that can be used for developing brighter light sources including the shape and aspect ratio of a heterojunction at the micro- or nanoscale.
Applied Physics Letters


External quantum efficiency, AlGaN, fin, light-emitting diode, nanoled, optical cavity, electroluminescence. cathodoluminescence.


Nikoobakht, B. , Zong, Y. , Koksal, O. , Agrawal, A. , Montgomery, C. , Leach, J. and Shur, M. (2023), Impact of fin aspect ratio on enhancement of external quantum efficiency in single AlGaN fin light-emitting diodes pixels, Applied Physics Letters, [online],, (Accessed May 24, 2024)


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Created June 26, 2023, Updated November 15, 2023