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.

Colloidal quantum dots which can emit red, green, and blue colors are incorporated with a micro-LED array to demonstrate a feasible choice for future display technology. The pitch of the micro-LED array is 40 μm, which is sufficient for high-resolution screen applications. The method that was used to spray the quantum dots in such tight space is called Aerosol Jet technology which uses atomizer and gas flow control to obtain uniform and controlled narrow spots. The ultra-violet LEDs are used in the array to excite the red, green and blue quantum dots on the top surface. To increase the utilization of the UV photons, a layer of distributed Bragg reflector was laid down on the device to reflect most of the leaked UV photons back to the quantum dot layers. With this mechanism, the enhanced luminous flux is 194% (blue), 173% (green) and 183% (red) more than that of the samples without the reflector. The luminous efficacy of radiation (LER) was measured under various currents and a value of 165 lm/Watt was recorded.

Here, we report the cw laser operation of electrically pumped GaN-based vertical cavity surface emitting laser (VCSEL). The GaN-based VCSEL has a ten-pair InGaN∕GaN multiple quantum well active layer embedded in a GaN hybrid microcavity of 5λ optical thickness with two high reflectivity mirrors provided by an epitaxially grown AlN∕GaN distributed Bragg reflector (DBR) and a Ta2O5∕SiO2 dielectric DBR. cw laser action was achieved at a threshold injection current of 1.4mA at 77K. The laser emitted a blue wavelength at 462nm with a narrow linewidth of about 0.15nm. The laser beam has a divergence angle of about 11.7° with a polarization ratio of 80%. A very strong spontaneous coupling efficiency of 7.5×10−2 was measured.

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