A passive matrix (PM) blue Micro light‐emitting diode (LED) device with 300 μm pixel size and 7/10/15/20/30/50/100 μm luminous area is designed. The 1 μm thick insulating layer composed of SiO2 is grown in four steps, which improves the quality of the insulating layer and reduces the risk of electrical leakage. The thick metal is used as the p lines and the n lines. The non‐conductive GaN is left as the structure underneath the p lines to alleviate the breakage of the p lines to improve the reliability of the device. The optimized technology is used to fabricate the micro‐display, and the optical and electrical characterization is carried out. Besides, we realize the character display. With no additional manufacturing process, this work will contribute to the implementation of highly reliable PM Micro‐LED display technology.

Micro-LEDs are one of the most promising candidates for next-generation displays, yet they are inconvenienced by the efficiency reduction induced by the sidewall defects when pursuing further scaled-down device dimensions. We have systematically investigated both the size and temporal dependence of micro-LEDs. Micro-LED arrays with a mesa size ranging from 7 to 100 μm were prepared for display purposes. The luminance and external quantum efficiency (EQE) were measured and discussed. Surprisingly, micro-LED arrays with a smaller mesa size exhibit a higher EQE under 100 ns pulse duration operation when compared with longer pulse duration operations. Under certain short-pulsed excitation, a 7×7  μm2 micro-LED array even exhibits a >20% higher EQE as compared to the direct current (DC) or the long duration pulse operation condition. We thus concluded that the notorious efficiency reduction induced by sidewall defects in small-sized micro-LED arrays could be significantly reduced by applying short-pulse voltages.

In this study, the STM32 microcontroller is used to drive a passive matrix (PM) Micro-LED through two-wire serial transmission and row-column integration. STM32 exhibits superior properties, including simple-to-operate, cost-friendly, and flexible programming. Moreover, it has a lower cost and more straightforward implementation for testing the quality of the device and realizing the graphics. In this design, the connection between the STM32 and the PM array is realized by an LED driver board and flexible printed circuit (FPC) structure. The two-wire serial protocol and row-column integration are adopted, which not only optimizes the circuit structure but also avoids coupling problems. Compared to the existing structures, it is more concise that only four connecting wires are required to transmit data in display devices of any resolution. Besides, the problem of graphics distortion is solved through two buffers to form a data handshake. Using this method, the blue PM array, which has a resolution of 48 × 48, a refresh rate of 60 Hz, a pixel size of 300 μm, and a luminous area of 50 μm, is successfully realized. In addition, p-metal fractures caused by the bulge in the p-lines are also resolved by adding the GaN as a raised substrate.