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Japan firm grows blue LED on wafer

Posted: 01 Jan 2007 ?? ?Print Version ?Bookmark and Share

Keywords:blue LED? LED? light emitting diode? silicon wafer? Shimei Semiconductor?

Japan's Shimei uses special process for GaN crystalline deposition on silicon.

Shimei Semiconductor Co. has grown a blue LED on a silicon wafer, potentially slashing the cost of such devices and easing their integration into CMOS circuits. Shimei plans to make the LED available by Q2.

Using silicon wafers as a substrate for GaN crystalline deposition could simplify the LED structure and extend the lifetime, as well as drastically lower the cost, the company said. Currently, sapphire substrates are widely used for GaN epitaxy.

"Silicon wafers have a lot of advantages," said Hirofumi Yamamoto, founder and chief technology officer of Shimei Semiconductor. "It is easy to make large-area LEDs, and drivers and other circuits can be fabricated on the same silicon substrate."

The prototype LED emits blue light of the 450nm wavelength and has an output power of 10mW. The device has a layered structure consisting of a cathode on the bottom, the silicon substrate, buffer layers, an emitting layer and an anode on top. As the silicon substrate absorbs light generated at the emitting layer, a reflective film is formed on the silicon to improve efficiency. Yamamoto said the buffer layers in the blue LED are different from conventional buffers. He declined to elaborate.

The company said a proprietary material composition and a special processmaterial organic chemical vapor phase epitaxial growthwere the enablers for accomplishing GaN epitaxy on silicon. Shimei said it is readying production lines with a monthly capacity of 3 million units and will start sampling in April. The blue LEDs will be supplied in bare-chip or wafer form.

- Yoshiko Hara
EE Times

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