Nitrides Seminar - Lesley Chan, Graduate Student Researcher, Chemical Engineering
11/19/2019 12PM ESB 1001
Lesley Chan Department of Chemical Engineering, University of California-Santa Barbara, Santa Barbara, CA
Colloidal lithography is a simple, scalable, and reproducible nanopatterning approach to create closepacked patterns of nano- and microscale features. In this talk, I will discuss two ways colloidal lithography, via Langmuir-Blodgett dip-coating, has been used in III-nitride light emitting diodes (LEDs). First, light outcoupling surface features were implemented on the substrate side of LED devices grown on freestanding semipolar (20-21) GaN substrates. 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. PL results also demonstrate that colloid-based roughening, which has greater geometric tunability and works on any GaN orientation, results in equivalent light extraction enhancement compared to current, c-plane only photoelectrochemical (PEC) roughening methods. The colloidal nanopatterning method was also adapted to create active nanoscale light emitters (nano-LEDs). In this work, LEDs with active and sacrificial MQW layers were epitaxially grown using MOCVD. Devices were fabricated and subsequently chemically released from the GaN growth substrate, into solution using a combination of colloidal nanopatterning and PEC etching of the sacrificial MQW layer. This work shows that colloidal lithography combined with PEC etching is a viable route to solution processable, high efficiency RGB light emitting platforms.