Analysis of Improved Efficiency of InGaN Light‐Emitting Diode With Bottom Photonic Crystal Fabricated by Anodized Aluminum Oxidxe

Abstract

The improved performance of a bottom photonic crystal (PC) light‐emitting diode (LED) is analyzed based on internal quantum efficiency (ηint) and light‐extraction efficiency (ηex). The bottom PC is fabricated by anodized aluminum oxide nanopatterns and InGaN quantum wells (QWs) are grown over it. Transmission electron microscopy images reveal that threading dislocations are blocked at the nanometer‐sized air holes, resulting in improved optical emission efficiency of the QWs. From temperature‐dependent photoluminescence measurements, the enhancement of ηint is estimated to be 12%. Moreover, the enhancement of ηex is simulated to be 7% by the finite‐difference time‐domain method. The fabricated bottom PC LED shows a 23% higher optical power than a reference, which is close to the summation of enhancements in ηint and ηex. Therefore, the bottom PC improves LED performance through higher optical quality of QWs as well as increased light extraction.

Temperature-dependent photoluminescence in light-emitting diodes

“…3(a). The temperature-dependent PL intensity can be well fitted using the following Arrhenius formula3243444546: where I(T) represents the normalized integrated PL intensity. The parameters C 1 and C 2 are two constants related to the density of non-radiative recombination centres in the samples.…”

“…Based on photoluminescence spectra measured at different temperatures, a systematic and mature theory has been developed to study the defects related to non-radiative processes3233, localized states2034, and carrier transport dynamics203536. A series of physical equations are widely used to characterise and fit the above physical processes.…”

“…The second approach is non-resonant excitation, in which the excitation energy is higher than the barrier band gap, and thus, both the barriers and the wells are excited373839. In previous reports, for both resonant excitation and non-resonant excitation, the Arrhenius formula and the band-tail model have been widely used to describe carrier transport and localized states, respectively, in quantum-well structures1920213233363739. However, these physical equations cannot accurately reflect the carrier transport and localized states for both excitation modes, and thus, they lead to an equivocal description of these physical processes.…”

Light extraction efficiency enhancement of flip-chip blue light-emitting diodes by anodic aluminum oxide

“…Huang et al used Zn and Mg for ion implantation at the GZO thin layer and then adopted rapid thermal annealing to enhance the LEE of short-wavelength purple and ultraviolet LEDs by 1.4–2.5 times that of a traditional LED [14]. Ryu et al adopted anodic aluminum oxide (AAO) to produce a photonic crystal structure at the n-GaN layer of LEDs, and transmission electron microscopy (TEM) images showed that screw dislocations in the LED structure were blocked, thus enhancing the general luminous efficiency by approximately 23% [15]. Cates et al adopted laser etching to produce a repeated microstructure on the emitting surface of a yttrium aluminum perovskite scintillation crystal activated by cerium (formula YAlO 3 :Ce, abbreviated as YAP:Ce) and reduced the total reflection of light via surface roughening.…”

Improvement of photon extraction efficiency of GaN-based LED using micro and nano complex polymer structures

“…Various attempts, including surface roughening [7,8], the formation of photonic crystals [9,10], the use of patterned sapphire substrates (PSS) [11,12], and the use of an air-gap structure inside the LED [13], were made to suppress the TIR.…”