Seoul Semi ends need for rare Earths in white LEDs
For three decades, white LEDs have depended on rare earth materials such as yttrium aluminum garnet (YAG) layered onto a blue LED chip. Seoul Viosys has now broken that dependence and is mass producing a chip that emits white light without rare earths. The chip can be as small as 10 µm.
Seoul Viosys and its parent company Seoul Semiconductor opened the microLED market with WICOP. WICOP is a chip architecture that eliminates the package altogether. Doing away with the package is widely regarded in the industry as a revolution in six decades of semiconductor history.
With WICOP, the two companies say they have already developed and mass produced ultraviolet, blue, green, red and infrared LEDs under 100 µm that are too small for the eye to see. WICOP 3 is the third generation of the technology. It now extends that capability to white light without rare earth elements (REEs).
White LEDs make up roughly $10 billion of the $15 billion global market for packaged LEDs. WICOP 3 can now replace them with a technology free of rare earths, according to Seoul Semi. More significant still, WICOP 3 is claimed to be the world's first white opto-semiconductor to achieve white light in a microLED smaller than 100 µm. At that size, it is invisible to the naked eye.
WICOP 3 uses neither rare earths nor package. The result is a far more environmentally friendly product that costs about half as much to make as a conventional white LED.
In its first mass production, a microLED chip measuring just 25 µm by 10 µm produced 0.015 lumens of white light. Its chromaticity falls inside the CIE standard white region. Luminous efficacy is already close to 100 lumens per watt (lm/W). The company aims to reach 200 lm/W within two years. A conventional 1,000 µm by 1,000 µm chip achieves 50 lumens.
Until now, WICOP could make chips smaller, but white light still required a package containing rare earths. White chips therefore could not go below 1,000 µm. This held back cost reduction. White microLEDs under 100 µm (0.1 mm) were also out of reach. Removing rare earths changes that. White light is now possible both in large chips of 1,000 µm and above and in microLEDs below 100 µm.
Seoul Viosys uses WICOP to produce micro opto-semiconductors below 100 µm. It says microLEDs built on WICOP can also now carry high volumes of AI data over distances from under 1 cm to tens of metres.
