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Silicon substrates give cheap devices

26 Jul 2002

LEDs and lasers based on silicon substrates promise low-cost production.

Growing optoelectronics devices on a silicon substrate offers a cheap manufacturing route compared to traditional substrates such as sapphire and silicon carbide. Recent announcements by three independent groups show that this method of production is set to become a reality.

A collaboration between RWTH Aachen and MOCVD equipment maker Aixtron, both of Germany, and the Stepanov Institute of Physics in Belarus has produced the first optically pumped blue laser chip on a silicon substrate. The device is based on the InGaN/GaN material system.

The laser emits at 447 nm and has a maximum operating temperature of 420 K. A low threshold current gives an output power of 8 W with a power density of 270 kW/cm2.

Japan-based Sanken and fellow LED maker UEC of Taiwan have also announced similar developments.

Sanken has produced LEDs that it says are 10 times brighter than any of its conventional products. Based on an AlGaInP-on-Si structure, the devices can emit in the red at 620 nm or in the yellow at 590 nm.

The new LEDs use large-area chip design to carry up to 40 times more current than the company's standard emitters. Depending on the drive current, luminous intensities of 37 or 74 lumens are available at 620 nm and 21 or 42 lumens at 590 nm.

Sanken says that samples will be available from October with commercial production expected by mid-2003.

UEC has also revealed a high-power LED based on AlGaInP. Using its patented metal bonding technology, the device offers a luminous flux in excess of 200 lumens from a single chip. Samples will be released by the end of the year.

UEC has also developed a resonant-cavity LED, which features an output power of 1.5 mW at 20 mA and has an operating voltage of 2 V.

Jacqueline Hewett is news reporter on Optics.org and Opto & Laser Europe magazine.

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