Results and Discussions According to the self-designed vertical Micro-LED epitaxial structure (Fig. 1), the structure and parameters of Micro-LEDs with different sizes are modeled by using Sentaurus TCAD simulation software (Fig. 2), and the switching voltage is about 2.9 V (Fig. 3). The radiation recombination rate of Micro-LEDs decreases with the decrease in size (Fig. 4), and the light extraction efficiency decreases with the decrease in Micro-LED size (Fig. 6). From the perspective of the influence of radiation recombination rate and light extraction efficiency on Micro-LED miniaturization (Table 1), the small-size effect will lead to the decrease in the luminous intensity of Micro-LED unit pixels. If we want to keep the luminous intensity of the Micro-LED unit pixel constant, it is necessary to reduce the loss of Micro-LEDs, and the switching loss is one of the key factors of Micro-LED loss. In other words, reducing the switching loss can improve the small size effect of Micro-LEDs. The brightness of a blue-green LED of 300 μm can reach 546862 cd/m² (Fig. 7). By improving the parameters (Table 2), designing the PMOS driving backplane, and bonding PMOS devices and Micro-LED devices through indium bumps (Fig. 10), we can draw the following conclusions according to the simulation of Micro-LEDs driven by PMOS driving circuit (Table 4). Compared with a single Micro-LED driven by PMOS, the Micro-LED driven by PMOS has a shorter switching delay time, less switching loss, and better driving effect. Compared with PMOS plus current limiting resistor driving single Micro-LED, direct PMOS driving single Micro-LED has a shorter switching delay time, less switching loss, and better driving effect. When a PMOS current limiting resistor is applied to drive a single Micro-LED, a smaller resistance of the connected current limiting resistor is often accompanied by a shorter switching delay time, less switching loss, and better driving effect. The Micro-LED with a blue-green light of 300 μm is used for experimental verification (Fig. 21), and the same conclusion is obtained.

Micro light emitting diode (Micro-LED) is a kind of self-emitting device, and its single pixel can produce high brightness, which can realize the control of each pixel and single-point light driving. It has a very broad application prospect. Micro-LED display surpasses the current mainstream liquid crystal display (LCD) and organic light-emitting diode (OLED) display in terms of power consumption, resolution, contrast, and lifetime, which represents significant progress in the display field. However, the application of Micro-LED still faces challenges such as small size effect, chip and backplane technology, and bonding and driving technology. In this research, we use simulation software to design the structure parameters of Micro-LEDs and light them up, design the PMOS driving backplane, explore the small-size effect of Micro-LEDs, and study how to optimize the driving to improve the small-size effect of Micro-LEDs. We hope that our research will help overcome the current challenges faced by Micro-LEDs and realize the large-scale use of Micro-LEDs as soon as possible.

In this paper, the optimization of driving is studied to improve the small size effect of Micro-LEDs. Firstly, the structure and parameters of Micro-LEDs of 10 μm, 38 μm, 100 μm, and 300 μm are modeled by the simulation software of Sentaurus TCAD, and the small-size effect of Micro-LEDs is explored through the change in Micro-LED switching loss caused by the change in radiation recombination rate and light-emitting efficiency under small size, and the Micro-LED of 300 μm blue-green light is lit. Next, a PMOS device of 0.18 μm is designed as the driving backplane through Sentaurus simulation, and the PMOS device and Micro-LED device are bonded through indium bumps. Then, the simulation of PMOS driving circuit driving a single Micro-LED, the simulation of PMOS plus current-limiting resistors with different resistance values driving a single Micro-LED, and the simulation of PMOS driving two Micro-LED pixels are carried out to simulate the driving of array pixels. Finally, the driving effect is judged by comparing the switching delay time, and the experimental verification is carried out by using a blue-green Micro-LED of 300 μm.

In this paper, the Micro-LED's small size effect is studied. It is found that with the decrease in Micro-LED's size, its radiation recombination rate, light output power, and light extraction efficiency gradually decrease, which leads to the decrease in Micro-LED's unit pixel luminous intensity. In order to keep the luminous intensity constant, it is necessary to reduce the Micro-LED's loss, and the switching loss is one of the key factors of Micro-LED's loss. In other words, reducing the switching loss can improve the Micro-LED's small size effect. In view of the small-size effect of Micro-LED, the process of driving Micro-LED by driving circuit is simulated, and the research on reducing switching loss is carried out. In this paper, a PMOS device of 0.18 μm is designed. The PMOS device and Micro-LED device are bonded by an indium bump, and the simulation of PMOS driving circuit driving single Micro-LED and array Micro-LED is carried out. By comparing the switching loss caused by switching delay time, the driving effect is judged. It is found that the Micro-LED driven by PMOS array has a shorter switching delay time, less switching loss, and better driving effect than that driven by PMOS alone. Compared with PMOS plus current limiting resistor driving single Micro-LED, direct PMOS driving single Micro-LED has a shorter switching delay time, less switching loss, and better driving effect. When a PMOS current limiting resistor is applied to drive a single Micro-LED, a smaller resistance of the connected current limiting resistor is often accompanied by a shorter switching delay time, less switching loss, and better driving effect.