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IMEC, Aixtron tout advance to low-cost GaN power apps

Posted: 05 Jun 2008 ?? ?Print Version ?Bookmark and Share

Keywords:GaN power device? AlGaN? silicon wafer?

IMEC and Aixtron AG researchers have grown uniform AlGaN/GaN heterostructures on 200mm silicon wafers. The achievement is claimed to be a major advance towards fabricating low-cost GaN power devices for high-efficiency/high-power systems beyond the silicon limits.

The researchers have deposited, for the first time, crack-free AlGaN/GaN structures on to 200mm Si(111) wafers. The layers show good crystalline quality as measured by high-resolution x-ray diffraction, and the researchers report "excellent" morphology and uniformity.

The AlGaN and GaN layers were grown in Aixtron's application laboratory on the 300mm CRIUS metal-organic chemical-vapor-phase epitaxy reactor.

"The demonstration of GaN growth on 200mm Si wafers is an important step towards processing GaN devices on large Si wafers," said Marianne Germain, program manager of IMEC's efficient power program. "There is a strong demand for GaN-based solid-state switching devices in the field of power conversion. However, bringing GaN devices to a level acceptable for most applications requires a drastic reduction in the cost of this technology. That is only possible by processing on large-diameter Si wafers. 150mm, and then 200mm are the minimum wafer sizes we need to fully leverage today's silicon processing capabilities."

Germain cautions the bow of the resulting wafers is still quite large, in the range of 100?m. But the researchers believe an optimized buffer can reduce this bow drastically, enabling further processing. "We aim to further develop the growth process and to qualify the wafers to be compatible with Si-CMOS process," she adds.

The 200mm wafers used were custom-made by MEMC Electronic Materials Inc. using the Czochralski growth method. A standard layer stack that had already been successfully demonstrated on 100- and 150mm Si (111) substrates was used for the AlGaN/GaN heterostructures.

An AlN layer was first deposited on to the Si substrate, followed by an AlGaN buffer that provided compressive stress in the 1 micron thick GaN top layer. The stack was finished with a 20nm thin AlGaN (26 percent Al) layer and capped with a 2nm GaN layer.

- John Walko
EE Times Europe





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