Improved optical and electrical properties of GaN-based micro light-emitting diode arrays

Light output power and current density of GaN-based blue light-emitting diodes (LEDs) were improved by using a micro-LED (μLED) array structure. The μLED array has the advantage of uniform current spreading, leading to effective current injection into multiple quantum wells. Arrays of 4 × 4 and 12 × 15 μLEDs with 130- and 30-μm pixel sizes were fabricated and compared with a large-area LED. Considering the emission area, the enhancement rates of the output power were as high as 174% and 116% at 300 mA for the 12 × 15 and 4 × 4 μLED arrays, respectively. For electrical properties, the current density of the 12 × 15 μLED array was enhanced by a factor of 2.1 compared to that of the reference large-area LED. These results were attributed to improvement in uniform current spreading, which was confirmed by calculating the current spreading equation. In addition, we demonstrated that finite-difference time-domain (FDTD) simulations can be conducted to theoretically confirm the light extraction effect of the μLED structure. In addition, the FDTD results reveal that the extraction ratio was enhanced by reducing the effect of total internal reflection when the μLED was used.