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17 Jun 2002
US-based TDI makes blue laser breakthrough after manufacturing gallium nitride bulk substrates.
Researchers at US-based Technology and Devices International (TDI) have created a gallium nitride (GaN) bulk substrate, which they say will improve the performance and lifetimes of GaN-based device designs. A single crystal GaN sample boule is grown on a GaN seed layer and then sliced into 1.5 inch diameter wafers.
While details of the wafer growth process are being withheld, TDI's chief executive Vladimir Dmitriev told Optics.Org's sister publication Compound Semiconductor that each boule yields several wafers. "The crystals are grown using a 1.5 inch GaN seed crystal and are expected to scale to 3 and 4 inches in the future," he added.
According to Dmitriev, independent research shows that the dislocation density of the wafers is several orders of magnitude lower than conventionally-grown wafers. TDI researchers are now developing crystal growth and wafer fabrication technology to commercialize the substrates, and hope to start pilot production in six months.
"This is a true breakthrough for group III nitride development," said Dmitriev. "Within one year, the bulk GaN could be the basis of blue-spectrum high-brightness light-emitting diodes."
Today's GaN wafers are epitaxially grown on sapphire or silicon carbide substrates, which are later removed to leave a free-standing GaN wafer. This process route leads to a high density of defects known as dislocations. These defects reduce a device's reliability, but by slicing wafers directly from a boule, TDI has side-stepped this problem.
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