Horizontally assembled green InGaN nanorod LEDs: scalable polarized surface emitting LEDs using electric-field assisted assembly.

Hoo Keun Park,Yun Jae Eo,Seong Woong Yoon,Ji Hye Oh,Won Woo Chung,Woong Kim,Young Rag Do,Gang Yeol Yoo,Keyong Nam Lee

doi:10.1038/srep28312

Abstract

In this study, we report the concerted fabrication process, which is easy to transform the size of active emitting area and produce polarized surface light, using the electric-field-assisted assembly for horizontally assembled many tiny nanorod LEDs between two metal electrodes. We fabricate the millions of individually separated 1D nanorod LEDs from 2D nanorod arrays using nanosphere lithography, etching and cutting process of InGaN/GaN LED structure on a flat sapphire substrate. The horizontally assembled InGaN-based nanorods LED device shows bright (~2,130 cd/m2) and uniform polarized (polarization ratio, ρ = ~0.61) green emissions from large area (0.7 cm × 0.6 cm) planar surface. The realization of a horizontally assembled nanorod LED device can prove the concept of an innovative idea to fabricate formable and scalable polarized surface LED lighting.

Highlights

To date, many reports regarding millimeter-size LED chips have focused on improving energy efficiency levels[1,2] and reducing efficiency droop[1,3] for applications to general lighting and giant outdoor displays
We propose the concerted fabrication of individually separated GaN-based nanorod LEDs as nano-emitters and the development of a horizontally assembled nano-LED system with millions of tiny nanorods that can be evolved into planar surface lighting or direct-view displays, as well as polarized light sources
This nano-LED approach cannot at this moment provide a perfect solution for the realization of highly efficient LED surface lighting and LED display using nanoscale LEDs, this concerted attempt at the creation of a concept for combining different fabrication approaches is considered to be an initial suggestion toward possible nanoscale LED devices that can be realized in the future

Summary

Introduction

Many reports regarding millimeter-size LED chips have focused on improving energy efficiency levels (i.e., both internal efficiency and extraction efficiency)[1,2] and reducing efficiency droop[1,3] for applications to general lighting and giant outdoor displays. Our technology is divided into three techniques: the first is a wafer-scale technology that combines bottom-up and top-down technologies to produce individually separated nanorod LEDs with InGaN/GaN multiple quantum wells (MQW); the second is a controlled dielectrophoretic assembly technology for millions of individually separated InGaN/GaN green-emitting nanorod LEDs as interconnected arrays on pre-patterned interdigitated electrodes; the third is an advanced interconnection scheme and horizontal device layout to facilitate electrical contact and system integration These concerted approaches allow the devices to be implemented in a wide range of scalable self-emissive polarized surface LED devices with large area (0.7 cm × 0.6 cm) for surface lighting or small pixel area (100 μm × 100 μm) for displays. This nano-LED approach cannot at this moment provide a perfect solution for the realization of highly efficient LED surface lighting and LED display using nanoscale LEDs, this concerted attempt at the creation of a concept for combining different fabrication approaches is considered to be an initial suggestion toward possible nanoscale LED devices that can be realized in the future

Methods

Results

Conclusion