Open AccessEnhanced light extraction from free-standing InGaN/GaN light emitters using bio-inspired backside surface structuring
Author(s) -
Christopher D. Pynn,
Lesley Chan,
Jorge Víctor Alcaráz Vera,
Alex Berry,
David J. Hwang,
Haoyang Wu,
Tal Margalith,
Daniel E. Morse,
Steven P. DenBaars,
Michael J. Gordon
Publication year - 2017
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.25.015778
Subject(s) - materials science , optoelectronics , lithography , colloidal crystal , etching (microfabrication) , nanoimprint lithography , light emitting diode , nanolithography , gallium nitride , optics , nanotechnology , colloid , layer (electronics) , chemistry , medicine , alternative medicine , physics , pathology , fabrication
Light extraction from InGaN/GaN-based multiple-quantum-well (MQW) light emitters is enhanced using a simple, scalable, and reproducible method to create hexagonally close-packed conical nano- and micro-scale features on the backside outcoupling surface. Colloidal lithography via Langmuir-Blodgett dip-coating using silica masks (d = 170-2530 nm) and Cl 2 /N 2 -based plasma etching produced features with aspect ratios of 3:1 on devices grown on semipolar GaN substrates. InGaN/GaN MQW structures were optically pumped at 266 nm and light extraction enhancement was quantified using angle-resolved photoluminescence. A 4.8-fold overall enhancement in light extraction (9-fold at normal incidence) relative to a flat outcoupling surface was achieved using a feature pitch of 2530 nm. This performance is on par with current photoelectrochemical (PEC) nitrogen-face roughening methods, which positions the technique as a strong alternative for backside structuring of c-plane devices. Also, because colloidal lithography functions independently of GaN crystal orientation, it is applicable to semipolar and nonpolar GaN devices, for which PEC roughening is ineffective.