Nitride Semiconductors of Japan reports that on Nov. 1, 2018, the company established and opened a fully owned subsidiary, Micro Nitride Co., Ltd. The new company, located in Tokushima, develops, manufactures, and sells micro UV LED chips for micro LED displays.
The company notes that in recent years, self-emissive OLED displays have been widely adopted for small display applications. However, according to the company, such displays suffer from a short lifetime and can be easily damaged by heat. Hence, the research and development work to mass produce mini and micro LED displays has begun.
Two Ways to Make Micro LEDs
Currently, micro LED displays are made in two ways. The first method uses red, blue and green LEDs. The second method employs blue LED excitation to excite red and green phosphors with blue LEDs.
However, with the three micro LED type, it is impossible to produce µ red chips because its material is fragile. Moreover, it is difficult to mount LED chips of different colors with different structures in high density. Their current, voltage, and reaction speeds are different, thereby complicating the control of each chip.
The µ Blue LED excitation method can integrate all mounted LED chips into µ blue LEDs. So, the difficulty of mounting is reduced, and the current and voltage can also be unified. The disadvantage of this method is due to the blue light coming from direct emission while the red light and the green light are come from excitation, causing a time lag in the reaction rate. Also, the color reproducibility is low because of the low luminance of red and green due to blue excitation.
Nitride Semiconductors Developed New Patented Micro LED Structure
Nitride Semiconductors says contends that combining a µUV-LED with RGB phosphors solves the these issues.The company also says it found that the luminous efficiency is doubled when fabricating µUV-LED chip with an SLS structure in both n and p layer. (Patent pending). The company says that this doubling results from the short distance that the diffusion current has to travel, a light emission recombination increase, and the internal quantum efficiency improves as the distance from the light emitting layer to the outside shortens. Ultimately, these performance factors also enhance the external quantum efficiency.