Nitride semiconductor material maker TDI has begun distributing 2-inch template InGaN substrates to interested customers, saying it is the first company able to do so.
Commercial production in volumes of thousands of wafers per month is scheduled for early 2008, after the company has scaled up template-based HVPE production at its Silver Spring, Maryland, site.
The InGaN is deposited onto TDI’s existing GaN-on-sapphire wafer products, allowing tailored doping and thickness control of the GaN layer for specific applications.
InGaN technology has played a starring role in the recent advances of GaN epitaxy, serving as the light-emitting regions in blue and subsequently white LEDs, and blue lasers. TDI says that InGaN substrates are needed to lattice-match more closely with such structures, and further boost device performance.
“Since the first demonstration of high-quality InGaN materials grown by HVPE in 2006, we have been receiving continuous requests from our customers regarding these new products, ” said Vladimir Dmitriev, the company’s president and CEO.
InGaN devices grown directly on GaN are adversely affected by strain arising from the mismatch between the two materials, especially when they have a high In content, such as in green LEDs.
“To make the substrate close in terms of lattice constant, we have introduced a layer of InGaN on top of GaN,” Dmitriev explained.
TDI says it can produce 6-inch and larger wafers, but initially it is sticking with the 2-inch wafer size favored by LED makers, its main target market.
The new substrates have also received interest from laser diode makers, which Dmitriev admits demand lower dislocation densities than TDI is currently able to attain. He says the figure is currently “almost the same” as the 107-108 level seen in its GaN templates, but is keen to improve it further, knowing the rewards could be great.
“Currently, there are no green laser diodes, ” Dmitriev pointed out. “One of the specific targets for this technology is to lower the number of defect densities to help resolve this.”