We discuss the main challenges for the fabrication of emerging microLED displays. We shown that microtube technology is very well adapted to these new kind of displays, since it provides both mechanical and electrical connection of the microLEDs on the receiving substrate. Also, we present a new fabrication approach, where an elementary unit consists of all-in-one-RBG MicroLEDs on CMOS driving circuit.

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In this report, we propose to enhance the hole injection efficiency by adjusting the barrier height of the p-type electron blocking layer (p-EBL) for ∼273 nm deep ultraviolet light-emitting diodes (DUV LEDs). The barrier height for the p-EBL is modified by employing a p-Al 0.60 Ga 0.40 N/ Al 0.50 Ga 0.50 N/p-Al 0.60 Ga 0.40 N structure, in which the very thin Al 0.50 Ga 0.50 N layer is able to achieve a high local hole concentration, which is very effective in reducing the effective barrier height of the p-EBL for holes. More importantly, besides the thermionic emission, such a p-EBL structure can also favor a strong intraband tunneling process for holes. As a result, we can obtain a more efficient hole injection into the quantum wells, leading to a remarkably improved optical power for the DUV LED with the proposed p-EBL architecture.

This work reports a nearly efficiency-droop-free AlGaN-based deep ultraviolet light-emitting diode (DUV LED) emitting in the peak wavelength of 270 nm. The DUV LED utilizes a specifically designed superlattice p-type electron blocking layer (p-EBL). The superlattice p-EBL enables a high hole concentration in the p-EBL which correspondingly increases the hole injection efficiency into the multiple quantum wells (MQWs). The enhanced hole concentration within the MQW region can more efficiently recombine with electrons in the way of favoring the radiative recombination, leading to a reduced electron leakage current level. As a result, the external quantum efficiency for the proposed DUV LED structure is increased by 100% and the nearly efficiency-droop-free DUV LED structure is obtained experimentally.

Visible Light Communication (VLC) technology is an emerging technology using visible light modulation that, in the modern world, will mainly facilitate high-speed internet connectivity. VLC provides tremendous advantages compared to conventional radio frequency, such as a higher transmission rate, high bandwidth, low-power consumption, no health hazards, less interference, etc., which make it more prominent in recent days. Due to their outstanding features, including low cost, low power consumption, etc., µ-light-emitting diodes (LEDs) have gained considerable attention for VLC implementation, but mostly for the ability to be used for lighting as well as communications. In this review paper, we will focus mainly on recent developments in VLC applications and various factors affecting the modulation bandwidth of VLC devices. Numerous factors, such as quantum confined stark effect (QCSE), carrier lifetime, carrier recombination time, crystal orientation, etc. affect the modulation bandwidth of LEDs, and more information will be discussed in the following sections. This paper will focus on VLC applications based on LEDs but mainly on semipolar μ-LEDs and μ-LED-based arrays with high bandwidths. Another important application of VLC is underwater optical wireless communication (UOWC), which has drawn a huge interest in marine exploration and underwater connectivity, but still faces some challenges because visible light is being used. In addition, this paper will focus on how the current VLC system modulation bandwidth can be enhanced. Many methods have been introduced, such as decreasing the active layer thickness or effective active area or using doping, but the bandwidth is restricted by the recombination time when the system configuration reaches its limit. Therefore, it is important to find alternative ways such as optimizing the system, using the blue filter or using the equalization technology, which will be addressed later. Overall, this review paper provides a brief overview of the VLC-based system performance and some of its potential prospects.