Enhancement of external quantum efficiency in GaN based LEDs

Jun Ho Son; Jong-Lam Lee

doi:10.1117/12.877041

3 March 2011 Enhancement of external quantum efficiency in GaN based LEDs

Jun Ho Son, Jong-Lam Lee

Proceedings Volume 7939, Gallium Nitride Materials and Devices VI; 79391D (2011) https://doi.org/10.1117/12.877041
Event: SPIE OPTO, 2011, San Francisco, California, United States

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.

Citation Download Citation

Jun Ho Son and Jong-Lam Lee "Enhancement of external quantum efficiency in GaN based LEDs", Proc. SPIE 7939, Gallium Nitride Materials and Devices VI, 79391D (3 March 2011); https://doi.org/10.1117/12.877041

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