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Optical devices to replace toxic lighting mechanisms

Taiwanese scientists and chip manufacturers have developed a highly efficient light emitting diode (LED) with a mirror substrate fabricated by wafer bonding to make photonic devices perform much better than existing ones, the National Science Council (NSC) said yesterday.

Tsay Chung-biau (蔡忠杓), director of the NSC's department of engineering and applied sciences, said yesterday that a two-year, NT$12-million research project on highly efficient LEDs had led to 14 patents, licensed in both Taiwan and the US, and more than 20 new manufacturing process technologies.

Tsay said that the research project's results made Taiwan capable of competing with world-class companies in related fields, such as the US-based Hewlett Packard, Japan-based Toshiba, and Germany-based Osram.

At a press conference held by the council in Taipei, Horng Ray-hua (洪瑞華), a professor at the Institute of Precision Engineering of National Chung Hsing University (NCHU), demonstrated epiwafers with high-efficiency LEDs with special mirror substrates fabricated by wafer-bonding technology.

According to Horng, related technologies make it possible to produce larger but cheaper LEDs with high thermal conductivity.

"Our technologies will solve the heat problems common to existing LEDs," Horng said.

Horng said the new red-light LEDs are about three times brighter than traditional ones. The manufacturing process can be carried out at lower temperatures, ranging from 350oC to 400oC; existing processes use temperatures higher than 600oC.

The technologies were developed jointly with researchers from Visual Photonics Epitaxy Co Ltd (VPEC), which shared 20 percent of project expenses. Late last year, VPEC became the first epiwafer supplier to ship high-brightness AlGaInP chips wafer-bonded to a silicon substrate to customers in Taiwan.

According to Jim Liu (劉進祥), director of VPEC's LED products division, customers have been fascinated by the improved heat dissipation of the wafer-bonding LED.

"Our products involving new LED technologies interest clients in Taiwan, South Korea, Japan and even China," Liu said.

Liu said products using the new LED include outdoor signboards, traffic lights, car brake lights, optical computer mouses and back-lit items.

"Optical devices involving high-efficiency LEDs with longer lifespans have the potential to replace existing fluorescent tubes that contain toxic mercury and other hazardous materials," NCHU materials engineering professor Wuu Dong-sing (武東星) said.

Wuu said the promotion of LED lighting keeps Taiwan in line with global environmental protection trends.

Recycling fluorescent tubes is a challenging task for Taiwan's government, as the Environmental Protection Administration initiated related recycling policies only in 2002.

Wuu predicted that the new products would be more competitive because the price of LEDs might be halved by 2010. By then, Wuu said, the LEDs' performance will have improved even further.

NSC officials said the council will keep funding related research to develop blue-light LED technologies.
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