Jan 13 (Wed): "Demonstration of InGaN Based High Efficiency Blue Microcavity LEDs with a Cavity Length of 112~290 nm," Joonho Back, ECE PhD Defense

https://ucsb.zoom.us/j/87830868954?pwd=a3BRVHFMUUFpdkZIbjNrTW1uRHJidz09

ABSTRACT:

III-nitride materials are widely used these days for display, visual light communication, and power electronics from wearable devices to large home appliances. Especially, III-nitride micron-sized light-emitting diodes (µLEDs) in display get wide attention because of its self-emissivity, small form factor and reliability. These characteristics make µLEDs as one of the best candidates for the next generation displays such as ultra-high resolution near-eye displays for augmented reality (AR) and virtual reality (VR) applications. Because µLEDs have advantages in lifetime, color gamut, form factor size and efficiency unlike the other displays, such as LCDs and OLED.

However, there are several issues with the conventional µLEDs, such as color mixing, color purity, emission directionality, temperature and color stability. In order to solve those problems of µLEDs in the displays, InGaN based blue, green and red microcavity light-emitting diodes (MC-LEDs) with a single mode emission are attracting more attention as potential alternatives. The advantages of MC-LEDs are spectral purity and thermal stability because the spectrum width and shape are determined by the overlap of the cavity mode and of the InGaN quantum well (QW) emission. Another advantage is that the emission of MC-LEDs is more directional than conventional LEDs. These advantages suggest MC-LEDs could be the best fit for display application.

High-efficiency blue InGaN-based semipolar (20-2-1) ultra-short MC-LEDs with a cavity length of 205 nm and 290 nm were demonstrated for the first time. A peak external quantum efficiency (EQE) of 7.3%, which value is almost same as 10% of conventional c-plane µLEDs with a device thickness of ~5 µm grown on sapphire substrate, was achieved. The emission wavelength is around 420~430 nm. In order to obtain high-efficiency MC-LEDs, a sidewall treatment was performed by using buffered hydrofluoric acid and phosphoric acid to remove the dry etching residue and the surface damage. The demonstration of MC-LEDs with a high EQE and a single mode emission should pave the way for the application to display and others. 

BIO:

Ph.D. candidate in Electrical and Computer Engineering, August 2020
Advisor: Shuji Nakamura
Solid state lighting & energy electronics center (SSLEEC), University of California, Santa Barbara, CA
Design and development of III-nitrides materials for optoelectronics, such as LEDs and VCSELs  

M.S. in Electrical and Computer Engineering, March 2017
Advisor: Shuji Nakamura
University of California, Santa Barbara, CA

B.S. in Electronic Engineering, Feb 2013
Dongguk University, Seoul, South Korea

Hosted by: Professor Shuji Nakamura

Submitted by: Joonho Back <joonho@ucsb.edu>