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Proceedings Paper

Enhancement of external quantum efficiency in GaN based LEDs
Author(s): Jun Ho Son; Jong-Lam Lee
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Paper Abstract

We present a review of the recent developments to enhance the external quantum efficiency (EQE) in GaN based vertical light-emitting diodes (V-LEDs). The combined use of quasi-photonic crystal and photochemical etching significantly improved the light extraction efficiency (LEE) of V-LEDs by a factor of 5. The enhancement of light output power by the nanotexturing of n-face n-GaN was remarkably influenced by reflectance of the p-contact. The enhanced LEE was also demonstrated by depositing a spontaneously formed MgO nano-pyramids and ZnO refractive-index modulation layer on the surface of V-LEDs, resulting in the increase of output power by 49 %, comparing with the V-LEDs with a flat n-GaN surface. The thermal stability of Ag-based p-type ohmic contact was siginficantly enhanced by addition of Cu, In, and Mg atoms to Ag layer, leading to high light reflectance and low contact resisitivity. Finally, we present a method of increasing light output power and suppressing efficiency droop in V-LEDs without modifying the epitaxial layers. These improvements are achieved by reducing the quantum-confined Stark effect by reducing piezoelectric polarization that results from compressive stress in GaN epilayer. This compressive stress is relaxed due to the external stress induced by an electro-plated Ni metal substrate.

Paper Details

Date Published: 3 March 2011
PDF: 12 pages
Proc. SPIE 7939, Gallium Nitride Materials and Devices VI, 79391D (3 March 2011); doi: 10.1117/12.877041
Show Author Affiliations
Jun Ho Son, Pohang Univ. of Science and Technology (Korea, Republic of)
Jong-Lam Lee, Pohang Univ. of Science and Technology (Korea, Republic of)

Published in SPIE Proceedings Vol. 7939:
Gallium Nitride Materials and Devices VI
Jen-Inn Chyi; Yasushi Nanishi; Hadis Morkoç; Joachim Piprek; Euijoon Yoon, Editor(s)

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