Title :
Angularly Uniform White Light-Emitting Diodes Using an Integrated Reflector Cup
Author :
Zhu, L. ; Wang, X.H. ; Lai, P.T. ; Choi, H.W.
Author_Institution :
Dept. of Electr. & Electron. Eng., Univ. of Hong Kong, Hong Kong, China
fDate :
4/1/2010 12:00:00 AM
Abstract :
We report on white light-emitting diodes (LEDs) with a truncated-conical (TC) geometry produced by laser micromachining. A blue LED was shaped into a circular disc with 50??-inclined sidewall using a modified laser micromachining setup. A layer of Al was coated onto the inclined sidewall and the bottom surface to form an integrated reflector. Due to the highly reflective mirror, laterally propagating photons are redirected into the upward direction, contributing to an increase of 21.7% of light intensity in the normal direction. With quantum dots applied to the surface, white light emission from this TC-LED structure demonstrated a 37% enhancement in color uniformity, compared with a conventional device.
Keywords :
III-V semiconductors; aluminium; antireflection coatings; colour; gallium compounds; indium compounds; integrated optics; laser beam machining; light emitting diodes; micromachining; mirrors; optical elements; quantum dots; wide band gap semiconductors; Al; InGaN-GaN; angularly uniform white light-emitting diodes; blue LED; coating; color uniformity; integrated reflector; integrated reflector cup; laser micromachining; photon propagation; quantum dots; reflective mirror; truncated-conical geometry; white light emission; Color uniformity; laser micromachining; light extraction; white light-emitting diode (LED);
Journal_Title :
Photonics Technology Letters, IEEE
DOI :
10.1109/LPT.2010.2041651
