Study on different isolation technology on the performance of blue micro-LEDs array applications.

In this study, a 3 × 3 blue micro-LED array with a pixel size of 10 × 10 µm2 and a pitch of 15 µm was fabricated on an epilayer grown on a sapphire substrate using metalorganic chemical vapor deposition technology. The fabrication process involved photolithography, wet and dry etching, E-beam evaporation, and ion implantation technology. Arsenic multi-energy implantation was utilized to replace the mesa etching for electrical isolation, where the implantation depth increased with the average energy. Different ion depth profiles had varying effects on electrical properties, such as forward current and leakage currents, potentially causing damage to the n-GaN layer and increasing the series resistance of the LEDs. As the implantation depth increased, the light output power and peak external quantum efficiency of the LEDs also increased, improving from 5.33 to 9.82%. However, the efficiency droop also increased from 46.3 to 48.6%.

Effects of ITO Contact Sizes on Performance of Blue Light MicroLEDs.

In this study, the effect of ITO contact ratio for blue light micro-light-emitting diode (µLED) with dimensions 40 µm × 40 µm was assessed. The contact ratio from 0.2 to 0.8 was designed for the ratio of electrode area to light-emitting area. As the contact ratio increased from 0.2 to 0.8, the turn-on voltage of µLED decreased. It could be due to the short lateral diffusion length in multiple quantum wells (MQW) and lower parallel resistance for the µLED with a large contact ratio. The leakage currents of single µLED were below 5.1 × 10-9 A, no matter the contact ratio. It means that the contact ratio does not affect the leakage current as measured on single chip. Moreover, µLED array with a 0.8 contact ratio presented the highest output power than other samples (5.25 mW as the current density of 1875 A/cm2). It could attribute to the MQWs usage, the metal contact reflective behavior and less current crowding, which generated more carriers and extracted more lighting from the µLED. The simulation data using SpeCLED software agreed well with these experiments, and µLED with a 0.8 contact ratio showed the best optoelectronic properties.