title: Light extraction enhancement with radiation pattern shaping of LEDs by waveguiding nanorods with impedance-matching tips.
abstract: Syringe-like ZnO nanorods (NRs) were fabricated on InGaN/GaN light emitting diodes (LEDs) by a hydrothermal method. Without sacrificing the electrical performances of LEDs, syringe-like NRs can enhance light extraction capability by 10.5% at 20 mA and shape the radiation profile with a view angle collimated from 136° to 121°. By performing optical experiments and simulation, it is found that the superior light extraction efficiency with a more collimated radiation pattern is attributed to the waveguiding effect of NRs and the mitigation of abrupt index change by the tapered ends of syringe-like ZnO NRs. This work demonstrates the importance of the nanostructure morphology in LED performances and provides the architecture design guidelines of nanostructures to a variety of optical devices.
authors.affiliation: Institute of Photonics and Optoelectronics & Department of Electrical Engineering, National Taiwan University, Taipei 10617, Taiwan. jhhe@cc.ee.ntu.edu.tw.
authors.forename: Yu-Hsuan
authors.initials: YH
authors.lastname: Hsiao
authors.forename: Cheng-Ying
authors.initials: CY
authors.lastname: Chen
authors.forename: Li-Chuan
authors.initials: LC
authors.lastname: Huang
authors.forename: Guan-Jhong
authors.initials: GJ
authors.lastname: Lin
authors.forename: Der-Hsien
authors.initials: DH
authors.lastname: Lien
authors.forename: Jian-Jang
authors.initials: JJ
authors.lastname: Huang
authors.forename: Jr-Hau
authors.initials: JH
authors.lastname: He