High-efficiency InGaN red micro-LEDs for visible light communication

Abstract

In this study, we present a high-efficiency InGaN red micro-LED fabricated by the incorporation of superlattice structure, atomic layer deposition passivation, and a distributed Bragg reflector, exhibiting maximum external quantum efficiency of 5.02% with a low efficiency droop corresponding to an injection current density of 112 A / cm 2 . The fast carrier dynamics in the InGaN is characterized by using time-resolved photoluminescence, which is correlated to a high modulation bandwidth of 271 MHz achieved by a 6 × 25-μm-sized micro-LED array with a data transmission rate of 350 Mbit/s at a high injection current density of 2000 A / cm 2 . It holds great promise for full-color micro-displays as well as high-speed visible light communication applications based on monolithic InGaN micro-LED technologies.

Modified Distributed Bragg Reflectors for Color Stability in InGaN Red Micro-LEDs

“…The central wavelength and FWHM of the EL mission as a function of current density for the InGaN red micro-LEDs with 1st and 2nd modified DBRs are shown in Figure 5 . As Figure 5 a shown, the peak position of the EL emission shows a blue shift of 16 nm which is much smaller than that in our previous work [ 36 ]. The FWHM of EL emission is broadened from 40 nm to 53 nm when the current density increased from 32 A/cm 2 to 400 A/cm 2 .…”

“…Even though there were several studies of InGaN red micro-LEDs, the EQE and the blue shift phenomenon of the device still have much room for improvement. In our previous work published in 2022 [ 36 ], a 25 µm-sized micro-LED was grown on a c-plane patterned sapphire substrate (PSS) by metal-organic vapor-phase epitaxy (MOVPE). The mainly epitaxial structures include an undoped-GaN layer to reduce the residual stress, 15 pairs of GaN/In 0.08 Ga 0.92 N superlattices (SL) layers, an InGaN blue single-quantum well (SQW), an InGaN red double-quantum well (DQWs) with a high indium content, a barrier layer, and contact layers.…”

“…Considering the chip size, the difficulty of processing, and the spectrum purity after the filter, a promising way to solve the problem of color shifting is to add a DBR as a color filter on the micro-LED which can completely block the shifting wavelengths. In this study, based on the experimental results of InGaN red micro-LED in our previous work [ 36 ], the modified DBRs were proposed as color filters of the InGaN red micro-LEDs ( Figure 2 ).…”

Recent Advances in Micro-LEDs Having Yellow–Green to Red Emission Wavelengths for Visible Light Communications

“…Although semipolar and m-plane micro-LEDs have excellent performance, the cost and difficulty of mass production make them challenging. As a result, in recent years, researchers have been studying ways to improve the performance of c-plane micro-LEDs, such as using strain-released layer [ 41 ], superlattice [ 56 ], and staggered quantum well [ 49 ].…”

“…Although the QCSE of the LEDs can be decreased by growing them on semipolar substrates, InGaN red micro-LEDs grown on c-plane substrates are currently the best option due to their compliance with existing manufacturing techniques. Recently in 2022, Huang et al demonstrated red-emitting InGaN-based micro-LED with high efficiency and high modulation bandwidth by incorporating superlattice structure and distributed Bragg reflector [ 56 ]. The epitaxial structure of the LED comprised blue InGaN single-QW (SQW) and red InGaN double-QWs (DQWs) as the active region.…”