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High Efficiency GaN-based Light Emitting Diodes with Embedded Air Voids/SiO2 Nanomasks

Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu, Taiwan, Republic of China.
Nanotechnology (Impact Factor: 3.67). 02/2012; 23(4):045303. DOI: 10.1088/0957-4484/23/4/045303
Source: PubMed

ABSTRACT In this paper, the high performance GaN-based light-emitting diodes (LEDs) with embedded microscale air voids and an SiO(2) nanomask by metal-organic chemical vapor deposition (MOCVD) were demonstrated. Microscale air voids and an SiO(2) nanomask were clearly observed at the interface between GaN nanorods (NRs) and the overgrown GaN layer by scanning electron microscopy (SEM). From the reflectance spectra we show strong reflectance differences due to the different refractive index gradient between the GaN grown on the nanotemplate and sapphire. It can increase the light extraction efficiency due to additional light scattering. The transmission electron microscopy (TEM) images show the threading dislocations were suppressed by nanoscale epitaxial lateral overgrowth (NELOG). The LEDs with embedded microscale air voids and an SiO(2) nanomask exhibit smaller reverse-bias current and large enhancement of the light output (65% at 20 mA) compared with conventional LEDs.

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    • "It is well known that one of the methods to reduce TDs and enhance the internal quantum efficiency of GaN-based LEDs is epitaxial lateral overgrowth (ELO). Light output enhancement of GaN-based LEDs through microscale or nanoscale ELO (NELO) have been reported for sapphire substrates [5], [6]. However, there are few reported device results for LEDs on Si substrates through the NELO method [7], especially for Manuscript received March 26, 2013; accepted April 20, 2013. "
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