Open AccessHigh efficiency ultraviolet GaN-based vertical light emitting diodes on 6-inch sapphire substrate using ex-situ sputtered AlN nucleation layer
Author(s) -
Jin Seok Oh,
Moon Youngjoo,
Dae Sung Kang,
Chan Keun Park,
Jung Soo Han,
Myung Hoon Jung,
Youngje Sung,
Hae Yong Jeong,
June O. Song,
Tae Yeon Seong
Publication year - 2018
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.26.005111
Subject(s) - materials science , sapphire , raman spectroscopy , in situ , nucleation , light emitting diode , substrate (aquarium) , optoelectronics , layer (electronics) , full width at half maximum , metalorganic vapour phase epitaxy , optics , analytical chemistry (journal) , laser , epitaxy , nanotechnology , chemistry , physics , oceanography , organic chemistry , chromatography , geology
We demonstrated the growth of crack-free high-quality GaN-based UV vertical LEDs (VLEDs) (λ = 365 nm) on 6-inch sapphire substrates by using an ex-situ sputtered AlN nucleation layer (NL) and compared their performance with that of UV VLEDs with an in situ low temperature (LT) AlGaN NL. The X-ray diffraction (XRD) results showed that the ex-situ AlN sample contained lower densities of screw-type and edge-type threading dislocations than the in situ AlGaN NL sample. The micro-Raman results revealed that the ex-situ AlN sample was under more compressive stress than the in situ AlGaN sample. As the current was increased, the electroluminescence peaks of both of the samples blue-shifted, reached a minimum wavelength at 1000 mA, and then slightly red-shifted. Packaged VLEDs with the ex-situ AlN NL yielded 6.5% higher light output power at 500 mA than that with the in situ AlGaN NL. The maximum EQEs of the VLED with the in situ AlGaN and ex-situ AlN NLs were 43.7% and 48.2%, respectively. Based on the XRD and Raman results, the improved light output power of the ex-situ AlN sample is attributed to the lower density of TDs.